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The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying base prospectus are not an offer to sell these securities, and we are not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Filed pursuant to Rule 424(b)(3)

SEC File No. 333-161923

(To Prospectus dated September 15, 2009)

5,000,000 Common Units

Representing Limited Partner Interests

5,000,000 common units representing limited partner interests in ONEOK Partners, L.P. are to be sold in this offering. We will receive all of the net proceeds from the sale of such common units.

Our common units are listed on the New York Stock Exchange under the symbol “OKS.” The last reported sale price of our common units on January 29, 2010 was $62.04 per unit.

Investing in our common units involves a high degree of risk. Before buying any common units, you should read the discussion of material risks of investing in our common units in “Risk factors” beginning on page S-8 of this prospectus supplement and on page 9 of the accompanying base prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved these common units or determined if this prospectus supplement or the accompanying base prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters may also purchase up to an additional 750,000 common units from us at the public offering price, less underwriting discounts and commissions payable by us, to cover over-allotments, if any, within 30 days from the date of this prospectus supplement. If the underwriters exercise the option in full, the total underwriting discounts and commissions will be $            , and the total proceeds, before expenses, to us from this offering will be $            .

The underwriters are offering the common units as set forth under “Underwriting.” Delivery of the common units will be made on or about February     , 2010.

Joint Book-Running Managers

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You should rely only on the information contained in or incorporated by reference into this prospectus supplement, the accompanying base prospectus and any free writing prospectus relating to this offering. We have not, and the underwriters have not, authorized anyone to provide you with additional or different information. If anyone provides you with additional, different or inconsistent information, you should not rely on it. You should not assume that the information contained in this prospectus supplement, the accompanying base prospectus, any free writing prospectus or the information we have previously filed with the Securities and Exchange Commission that is incorporated by reference herein is accurate as of any date other than its respective date. This prospectus supplement, the accompanying base prospectus and any free writing prospectus do not constitute an offer to sell or a solicitation of an offer to buy securities in any jurisdiction or to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction.

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This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering. The second part is the accompanying base prospectus, which gives more general information, some of which may not apply to this offering of common units. Generally, when we refer only to the “prospectus,” we are referring to both parts combined. If information varies between this prospectus supplement and the accompanying base prospectus, you should rely on the information in this prospectus supplement.

Any statement made in this prospectus supplement or in a document incorporated or deemed to be incorporated by reference into this prospectus supplement will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or in any other subsequently filed document that is also incorporated by reference into this prospectus supplement modifies or supersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement. Please read “Where you can find more information” and “Incorporation by reference” in this prospectus supplement and the accompanying base prospectus.

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Risk factors

An investment in our common units involves risks. You should also consider the risks that could affect us and our business. Although we have tried to discuss key factors, you need to be aware that other risks may prove to be important in the future. New risks may emerge at any time, and we cannot predict such risks or estimate the extent to which they may affect our financial performance. You should carefully consider the discussion of risks and the other information included or incorporated by reference in this prospectus supplement, including “Forward-looking statements,” as well as the discussion of risk factors in the accompanying base prospectus, under Part I, Item 1A in our Annual Report on Form 10-K for the year ended December 31, 2008, and under Part II, Item 1A in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2009, June 30, 2009, and September 30, 2009, each of which is incorporated by reference herein, before making a decision to invest in our common units.

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Use of proceeds

We expect to receive approximately $             million from the sale of our common units, or $             million if the underwriters exercise in full their over-allotment option to purchase additional common units, in each case, after deducting underwriting discounts and commissions and offering expenses payable by us. We intend to use the net proceeds we receive from this offering to repay amounts outstanding under our $1.0 billion revolving credit agreement and for general partnership purposes. As of January 29, 2010, the outstanding balance under our $1.0 billion revolving credit agreement was $465.0 million. Any amounts repaid under our $1.0 billion revolving credit agreement may be reborrowed by us and used for general partnership purposes. Affiliates of certain of the underwriters in this offering are lenders under our $1.0 billion revolving credit agreement and, as such, may receive a portion of the net proceeds from this offering. The average interest rate of borrowings under this agreement was 2.13% at December 31, 2009 and 2.64% at September 30, 2009. The $1.0 billion revolving credit agreement matures in March 2012. In addition, in conjunction with this offering, ONEOK Partners GP, L.L.C. will make a capital contribution of $             million so as to maintain its 2% general partner interest. ONEOK Partners GP, L.L.C.’s contribution will be used for general partnership purposes.

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Capitalization

The following table sets forth our capitalization as of September 30, 2009 on:

This table should be read in conjunction with our historical consolidated financial statements and the notes to those financial statements that are incorporated by reference into this prospectus supplement and the accompanying base prospectus. You should also read this table in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operation” in our Annual Report on Form 10-K for the year ended December 31, 2008 and in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2009, June 30, 2009, and September 30, 2009, each of which is incorporated by reference herein.

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Price range of common units and distributions

Our common units are listed on the NYSE under the symbol “OKS.” As of January 29, 2010 there were 59,912,777 common units outstanding, held by approximately 763 registered holders, and 36,494,126 Class B units outstanding. As of January 29, 2010, ONEOK, Inc. directly held all of our Class B units.

The following table sets forth, for the periods indicated, the high and low closing prices for our common units, as reported on the NYSE, and quarterly declared cash distributions on our common units for the quarter for which they are payable. The last reported sale price of our units on the NYSE on January 29, 2010 was $62.04 per common unit.

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Conflicts of interest

We are managed under the direction of the Board of Directors of our sole general partner, ONEOK Partners GP, L.L.C. Our general partner’s Board of Directors establishes our business policies. ONEOK, Inc. appoints the directors of our general partner and may change the composition or size of our general partner’s board at its discretion.

ONEOK, Inc., which is the parent company of our general partner, and its affiliates currently engage or may engage in the businesses in which we engage or in which we may engage in the future and neither ONEOK, Inc. nor any of its affiliates has any obligation to present business opportunities to us.

ONEOK, Inc. and its other affiliates may from time to time engage in transactions with us. As a result, conflicts of interest may arise between ONEOK, Inc. and its other affiliates, and us. If such conflicts arise then, in accordance with the provisions of our partnership agreement, the members of our general partner’s Board of Directors may themselves resolve such conflicts or may seek to have such conflicts of interest approved by either our conflicts committee (comprised of independent members of our general partner’s Board of Directors) and / or by a vote of unitholders.

Unless otherwise provided for in a partnership agreement, the laws of Delaware generally require a general partner of a partnership to adhere to fiduciary duty standards under which it owes its partners the highest duties of good faith, fairness and loyalty. Similar rules apply to persons serving on our general partner’s Board of Directors. Because of the competing interests identified above, our partnership agreement contains provisions that modify or in some cases eliminate certain of these fiduciary duties.

We are required to indemnify our general partner, the members of its Board of Directors, and its affiliates and their respective officers, directors, employees, agents and trustees to the fullest extent permitted by law against liabilities, costs and expenses incurred by any such person who acted in good faith and in a manner reasonably believed to be in, or (in the case of a person other than our general partner) not opposed to, our best interests and with respect to any criminal proceedings, had no reasonable cause to believe the conduct was unlawful.

Insofar as indemnification for liabilities arising under the Securities Act of 1933, as amended, may be permitted to directors, officers or persons controlling us pursuant to the foregoing provisions or otherwise, we have been advised that in the opinion of the Securities and Exchange Commission, such indemnification is against public policy as expressed in the Securities Act of 1933, as amended, and is, therefore, unenforceable.

Refer to the “Risk Factors” and the discussion of conflicts of interest in our Annual Report on Form 10-K for the year ended December 31, 2008, incorporated by reference herein, for additional information.

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Material tax considerations

The tax consequences to you of an investment in our common units will depend in part on your own tax circumstances. For a discussion of the principal federal income tax considerations associated with our operations and the purchase, ownership and disposition of our common units, please read “Material United States Federal Income Tax Considerations” in the accompanying base prospectus. Please also read “Item 1A. Risk Factors—Tax Risks” in our Annual Report on Form 10-K for the year ended December 31, 2008 for a discussion of the tax risks related to purchasing and owning our common units. You are urged to consult with your own tax advisor about the federal, state, local and foreign tax consequences peculiar to your circumstances.

PARTNERSHIP STATUS

The anticipated after-tax economic benefit of an investment in our common units depends largely on our being treated as a partnership for federal income tax purposes. We have not requested, and do not plan to request, a ruling from the IRS with respect to our classification as a partnership for federal income tax purposes. In order to be treated as a partnership for federal income tax purposes, at least 90% of our gross income must be from specific qualifying sources, such as the transportation, storage, processing and marketing of crude oil, natural gas and products thereof or other passive types of income such as interest (other than from a financial business) and dividends. For a more complete description of this qualifying income requirement, please read “Material United States Federal Income Tax Considerations—Partnership Status” in the accompanying base prospectus.

If we were treated as a corporation for federal income tax purposes, we would pay federal income tax on our taxable income at the corporate tax rate, which is currently a maximum of 35%, and would likely pay state taxes at varying rates. Distributions to you would generally be taxed again as corporate distributions, and no income, gains, losses or deductions would flow through to you. Because a tax would be imposed upon us as a corporation, our cash available for distribution to you would be substantially reduced. Therefore, treatment of us as a corporation would result in a material reduction in the anticipated cash flow and after-tax return to the unitholders, likely causing a substantial reduction in the value of our common units.

RATIO OF TAXABLE INCOME TO DISTRIBUTIONS

We estimate that a purchaser of common units in this offering who owns those common units from the date of closing of this offering through the record date for distributions with respect to the quarter ending December 31, 2012, will be allocated, on a cumulative basis, an amount of federal taxable income for the taxable years 2010 through 2012 that will be 20% or less of the total amount of cash distributed to the unitholder with respect to that period. Thereafter, we anticipate that the ratio of allocable taxable income to cash distributions to the unitholders will increase. These estimates are based upon many assumptions regarding our business and operations, including assumptions with respect to capital expenditures, cash flow and anticipated cash distributions. These estimates and assumptions are subject to, among other things, numerous business, economic, regulatory, legislative, competitive and political uncertainties beyond our control. Further, the estimates are based on current tax law and tax reporting positions that we have adopted and with which the IRS could disagree. Accordingly, we cannot assure you that these estimates will prove to be correct. The actual percentage of distributions that will constitute taxable income could be higher or lower, and any differences could be material and could materially affect the value of the common units.

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Material tax considerations

STATE, LOCAL AND OTHER TAX CONSIDERATIONS

In addition to federal income taxes, a unitholder will likely be subject to other taxes, such as state and local income taxes, unincorporated business taxes, and estate, inheritance or intangible taxes that may be imposed by the various jurisdictions in which we do business or own property or in which a unitholder is a resident. Each prospective unitholder should consider the potential impact of these various taxes on his investment in us. Although you may not be required to file a return and pay taxes in some jurisdictions if your income from that jurisdiction falls below the filing and payment requirement, you will be required to file income tax returns and to pay income taxes in many of the jurisdictions in which we do business or own property and may be subject to penalties for failure to comply with those requirements. In some jurisdictions, tax losses may not produce a tax benefit in the year incurred and may not be available to offset income in subsequent taxable years.

We determine our depreciation and cost recovery allowances using federal income tax methods and may use methods that result in the largest deductions being taken in the early years after assets are placed in service. Some of the jurisdictions in which we do business or own property may not conform to these federal depreciation methods. A successful challenge to these methods could adversely affect the amount of taxable income or loss being allocated to our unitholders for state tax purposes. It also could affect the amount of gain from a unitholder’s sale of common units and could have a negative impact on the value of the common units or result in audit adjustments to the unitholder’s state tax returns. Some of the jurisdictions may require us, or we may elect, to withhold a percentage of income from amounts to be distributed to a unitholder who is not a resident of the jurisdiction. Withholding, the amount of which may be greater or less than a particular unitholder’s income tax liability to the jurisdiction, generally does not relieve a non-resident unitholder from the obligation to file an income tax return. Amounts withheld will be treated as if distributed to unitholders for purposes of determining the amounts distributed by us. Please read “Material United States Federal Income Tax Considerations—Tax Consequences of Common Unit Ownership—Entity-Level Collections” in the accompanying base prospectus.

It is each unitholder’s responsibility to file all state and local, as well as U.S. federal, tax returns that may be required. Our counsel has not rendered an opinion on the state and local tax consequences of an investment in our common units. Accordingly, you are urged to consult with your own tax advisor with regard to those matters.

TAX EXEMPT ORGANIZATIONS AND OTHER INVESTORS

Ownership of common units by tax-exempt entities and non-U.S. investors raises issues unique to such persons. Please read “Material United States Federal Income Tax Considerations—Tax-Exempt Organizations and Other Investors” in the accompanying base prospectus.

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Underwriting

We are offering the common units described in this prospectus supplement through the underwriters named below. UBS Securities LLC, Merrill Lynch, Pierce, Fenner & Smith Incorporated, Citigroup Global Markets Inc., Morgan Stanley & Co. Incorporated and Wells Fargo Securities, LLC are the representatives of the underwriters and are acting as book-running managers of this offering. We have entered into an underwriting agreement with the representatives on behalf of the underwriters. Subject to the terms and conditions of the underwriting agreement, each of the underwriters has severally agreed to purchase the number of common units listed next to its name in the following table:

The underwriting agreement provides that the underwriters must buy all of the common units if they buy any of them. However, the underwriters are not required to take or pay for the common units covered by the underwriters’ over-allotment option described below.

Our common units are offered subject to a number of conditions, including:

In connection with this offering, certain of the underwriters or securities dealers may distribute prospectuses electronically.

OVER-ALLOTMENT OPTION

We have granted the underwriters an option to buy up to an aggregate of 750,000 additional common units. The underwriters may exercise this option solely for the purpose of covering over-allotments, if any, made in connection with this offering. The underwriters have 30 days from the date of this prospectus supplement to exercise this option. If the underwriters exercise this option, they will each purchase additional common units approximately in proportion to the amounts specified in the table above.

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Underwriting

COMMISSIONS AND DISCOUNTS

Common units sold by the underwriters to the public will initially be offered at the offering price set forth on the cover of this prospectus supplement. Any common units sold by the underwriters to securities dealers may be sold at a discount of up to $             per common unit from the public offering price. If all the common units are not sold at the public offering price, the representatives may change the offering price and the other selling terms. Upon execution of the underwriting agreement, the underwriters will be obligated to purchase the common units at the price and upon the terms stated therein, and, as a result, will thereafter bear any risk associated with changing the offering price to the public or other selling terms.

The following table shows the per common unit and total underwriting discounts and commissions we will pay to the underwriters assuming both no exercise and full exercise of the underwriters’ option to purchase up to an additional 750,000 common units.

We estimate that the total expenses of this offering payable by us, not including the underwriting discounts and commissions, will be approximately $400,000.

NO SALES OF SIMILAR SECURITIES

We, ONEOK, Inc., and the executive officers and directors of our sole general partner, ONEOK Partners GP, L.L.C., have entered into lock-up agreements with the underwriters. Under these agreements, subject to certain exceptions, we and each of the other previously listed persons may not, without the prior written approval of the representatives of the underwriters, offer, sell, contract to sell or otherwise dispose of, directly or indirectly, or hedge our common units or securities convertible into or exercisable or exchangeable for our common units. These restrictions will be in effect for a period of 90 days after the date of this prospectus supplement. At any time and without public notice, the representatives of the underwriters may, in their sole discretion, release some or all of the securities from these lock-up agreements.

If:

then the 90-day lock-up period will be extended until the expiration of the date that is 15 calendar days plus 3 business days after the date on which the issuance of the earnings release or the material news or material event occurs.

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Underwriting

INDEMNIFICATION AND CONTRIBUTION

We have agreed to indemnify the several underwriters and their controlling persons against certain liabilities, including certain liabilities under the Securities Act of 1933, as amended. If we are unable to provide this indemnification, we have agreed to contribute to payments the underwriters and their controlling persons may be required to make in respect of those liabilities.

NEW YORK STOCK EXCHANGE LISTING

Our common units are listed on the NYSE under the symbol “OKS.”

PRICE STABILIZATION, SHORT POSITIONS

In connection with this offering, the underwriters may engage in activities that stabilize, maintain or otherwise affect the price of our common units, including:

Stabilizing transactions consist of bids or purchases made for the purpose of preventing or retarding a decline in the market price of our common units while this offering is in progress. These transactions may also include making short sales of our common units, which involve the sale by the underwriters of a greater number of common units than they are required to purchase in this offering. Short sales may be “covered short sales,” which are short positions in an amount not greater than the underwriters’ over-allotment option referred to above, or may be “naked short sales,” which are short positions in excess of that amount.

The underwriters may close out any covered short position either by exercising their over-allotment option, in whole or in part, or by purchasing common units in the open market. In making this determination, the underwriters will consider, among other things, the price of common units available for purchase in the open market as compared to the price at which they may purchase common units through the over-allotment option.

Naked short sales are in excess of the over-allotment option. The underwriters must close out any naked short position by purchasing common units in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common units in the open market that could adversely affect investors who purchased in this offering.

The underwriters also may impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representatives have repurchased common units sold by or for the account of that underwriter in stabilizing or short covering transactions.

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Underwriting

As a result of these activities, the price of our common units may be higher than the price that otherwise might exist in the open market. If these activities are commenced, they may be discontinued by the underwriters at any time. The underwriters may carry out these transactions on the NYSE, in the over-the-counter market or otherwise.

ELECTRONIC DISTRIBUTION

A prospectus in electronic format may be made available on the Internet sites or through other online services maintained by one or more of the underwriters and/or selling group members participating in this offering, or by their affiliates. In those cases, prospective investors may view offering terms online and, depending upon the particular underwriter or selling group member, prospective investors may be allowed to place orders online. The underwriters may agree with us to allocate a specific number of common units for sale to online brokerage account holders. Any such allocation for online distributions will be made by the representatives on the same basis as other allocations.

Other than the prospectus in electronic format, the information on any underwriter’s or selling group member’s website and any information contained in any other website maintained by an underwriter or selling group member is not part of the prospectus or the registration statement of which this prospectus supplement and the accompanying base prospectus forms a part, has not been approved and/or endorsed by us or any underwriter or selling group member in its capacity as underwriter or selling group member and should not be relied upon by investors.

AFFILIATIONS

The underwriters and their affiliates have provided in the past and may provide from time to time in the future certain commercial banking, financial advisory, investment banking and other services for us for which they will receive customary fees. As described in “Use of proceeds,” some of the net proceeds of this offering may be used to pay down borrowings under our $1.0 billion revolving credit agreement. Affiliates of certain of the underwriters are lenders under such revolving credit agreement and will receive their respective share of any repayment by us of amounts outstanding thereunder. Because FINRA views our common units as interests in a direct participation program, this offering is being made in compliance with Rule 2310 of the FINRA Conduct Rules.

In the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers and may at any time hold long and short positions in such securities and instruments. Such investment and securities activities may involve securities and instruments of the issuer.

NOTICE TO INVESTORS

EUROPEAN ECONOMIC AREA

In relation to each Member State of the European Economic Area, or EEA, which has implemented the Prospectus Directive (each, a “Relevant Member State”), with effect from, and including, the date on which the Prospectus Directive is implemented in that Relevant Member State (the “Relevant Implementation Date”), an offer to the public of our securities which are the subject of the offering contemplated by this prospectus may not be made in that Relevant Member State, except that, with

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effect from, and including, the Relevant Implementation Date, an offer to the public in that Relevant Member State of our securities may be made at any time under the following exemptions under the Prospectus Directive, if they have been implemented in that Relevant Member State:

As used above, the expression “offered to the public” in relation to any of our securities in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and our securities to be offered so as to enable an investor to decide to purchase or subscribe for our securities, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State and the expression “Prospectus Directive” means Directive 2003/71/EC and includes any relevant implementing measure in each Relevant Member State.

The EEA selling restriction is in addition to any other selling restrictions set out in this prospectus.

GERMANY

This document has not been prepared in accordance with the requirements for a securities or sales prospectus under the German Securities Prospectus Act (Wertpapierprospektgesetz), the German Sales Prospectus Act (Verkaufsprospektgesetz), or the German Investment Act (Investmentgesetz). Neither the German Federal Financial Services Supervisory Authority (Bundesanstalt für Finanzdienstleistungsaufsicht - BaFin) nor any other German authority has been notified of the intention to distribute the common units in Germany. Consequently, the common units may not be distributed in Germany by way of public offering, public advertisement or in any similar manner AND THIS DOCUMENT AND ANY OTHER DOCUMENT RELATING TO THE OFFERING, AS WELL AS INFORMATION OR STATEMENTS CONTAINED THEREIN, MAY NOT BE SUPPLIED TO THE PUBLIC IN GERMANY OR USED IN CONNECTION WITH ANY OFFER FOR SUBSCRIPTION OF THE COMMON UNITS TO THE PUBLIC IN GERMANY OR ANY OTHER MEANS OF PUBLIC MARKETING. The common units are being offered and sold in Germany only to qualified investors which are referred to in Section 3, paragraph 2 no. 1, in connection with Section 2, no. 6, of the German Securities Prospectus Act, Section 8f paragraph 2 no. 4 of the German Sales Prospectus Act, and in Section 2 paragraph 11 sentence 2 no.1 of the German Investment Act. This document is strictly for use of the person who has received it. It may not be forwarded to other persons or published in Germany.

SWITZERLAND

The common units may not be publicly offered, distributed or re-distributed on a professional basis in or from Switzerland and neither this document nor any other solicitation for investments in the common units may be communicated or distributed in Switzerland in any way that could constitute a public

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offering within the meaning of Articles 1156/652a of the Swiss Code of Obligations (“CO”). This document may not be copied, reproduced, distributed or passed on to others without the Offeror’s prior written consent. This document is not a prospectus within the meaning of Articles 1156/652a CO and the common units will not be listed on the SIX Swiss Exchange. Therefore, this document may not comply with the disclosure standards of the CO and/or the listing rules (including any prospectus schemes) of the SIX Swiss Exchange. In addition, it cannot be excluded that the Offeror could qualify as a foreign collective investment scheme pursuant to Article 119 para. 2 Swiss Federal Act on Collective Investment Schemes (“CISA”). The common units will not be licensed for public distribution in and from Switzerland. Therefore, the common units may only be offered and sold to so-called “qualified investors” in accordance with the private placement exemptions pursuant to applicable Swiss law (in particular, Article 10 para. 3 CISA and Article 6 of the implementing ordinance to the CISA). The Offeror has not been licensed and is not subject to the supervision of the Swiss Financial Market Supervisory Authority (“FINMA”). Therefore, investors in the common units do not benefit from the specific investor protection provided by CISA and the supervision of the FINMA.

UNITED KINGDOM

This prospectus is only being distributed to and is only directed at: (1) persons who are outside the United Kingdom; (2) investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the “Order”); or (3) high net worth companies, and other persons to whom it may lawfully be communicated, falling within Article 49(2)(a) to (d) of the Order (all such persons falling within (1)-(3) together being referred to as “relevant persons”). The common units are only available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire such common units will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this prospectus or any of its contents.

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Legal matters

The validity of the common units being offered hereunder is being passed upon for us by Fried, Frank, Harris, Shriver & Jacobson LLP, New York, New York. Certain other legal matters will be passed upon for us by Gable & Gotwals, A Professional Corporation, Tulsa, Oklahoma, and certain tax matters will be passed upon for us by Andrews Kurth LLP, Houston, Texas. Certain legal matters will be passed upon for the underwriters by Shearman & Sterling LLP.

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Experts

The consolidated financial statements of ONEOK Partners, L.P. as of and for the years ended December 31, 2008 and 2007, management’s assessment of the effectiveness of internal control over financial reporting as of December 31, 2008 (which is included in Management’s Report on Internal Control over Financial Reporting) and the consolidated balance sheet of ONEOK Partners GP, L.L.C. as of December 31, 2008 incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2008, have been so incorporated in reliance on the reports of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The consolidated statements of income, cash flows, and changes in partners’ equity and comprehensive income of ONEOK Partners, L.P. (formerly Northern Border Partners, L.P.) for the year ended December 31, 2006 have been incorporated by reference herein in reliance upon the report of KPMG LLP, an independent registered public accounting firm, incorporated by reference herein, given on the authority of said firm as experts in auditing and accounting.

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Forward-looking statements

Some of the statements contained or incorporated in this prospectus supplement are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. The forward-looking statements relate to our anticipated financial performance, management’s plans and objectives for our future operations, our business prospects, the outcome of regulatory and legal proceedings, market conditions and other matters. We make these forward-looking statements in reliance on the safe harbor protections provided under the Private Securities Litigation Reform Act of 1995. The following discussion is intended to identify important factors that could cause future outcomes to differ materially from those set forth in the forward-looking statements.

Forward-looking statements include the items identified in the preceding paragraph, the information concerning possible or assumed future results of our operations and other statements contained or incorporated in this prospectus supplement identified by words such as “anticipate,” “estimate,” “plan,” “expect,” “forecast,” “guidance,” “intend,” “believe,” “should,” “project,” “goal,” “could,” “may,” “continue,” “might,” “potential,” “scheduled” and other words and terms of similar meaning.

You should not place undue reliance on forward-looking statements, which speak only as of the date of this prospectus supplement, or, in the case of documents incorporated by reference, the date of those documents. Known and unknown risks, uncertainties and other factors may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by forward-looking statements. Many of those factors that will determine these results are beyond our ability to control or predict. Those factors may affect our operations, markets, products, services and prices. In addition to any assumptions and other factors referred to specifically in connection with the forward-looking statements, factors that could cause our actual results to differ materially from those contemplated in any forward-looking statement include, among others, the following:

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Forward-looking statements

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Forward-looking statements

These factors are not necessarily all of the important factors that could cause actual results to differ materially from those expressed in any of our forward-looking statements. Other factors could also have material adverse effects on our future results. These and other risks are described in greater detail under the caption “Risk factors” in this prospectus supplement, in our Annual Report on Form 10-K for the year ended December 31, 2008 and in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2009, June 30, 2009, and September 30, 2009, each of which have been filed with the Securities and Exchange Commission and are incorporated herein by reference. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by these factors. Other than as required under securities laws, we undertake no obligation to update publicly any forward-looking statement, whether as a result of new information, subsequent events or change in circumstances, expectations or otherwise.

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Where you can find more information

We file annual, quarterly and other reports and other information with the Securities and Exchange Commission, or the SEC, under the Securities Exchange Act of 1934, as amended, or the Exchange Act. You may read and copy any materials we file with the SEC at the SEC’s public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room. Our SEC filings are also available to the public through the SEC website at http://www.sec.gov. General information about us, including our annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, as well as any amendments and exhibits to those reports, are available free of charge through our website at www.oneokpartners.com as soon as reasonably practicable after we file them with, or furnish them to, the SEC. Information on our website is not incorporated into this prospectus supplement or our other securities filings and is not a part of such filings. You can also inspect reports, proxy statements and other information about us at the offices of the NYSE, located at 20 Broad Street, New York, New York 10005.

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Incorporation by reference

The SEC allows us to “incorporate by reference” information into this document. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus supplement, and information that we file later with the SEC will automatically update and supersede the previously filed information. We incorporate by reference the documents listed below and any future filings made by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, other than any portions of the respective filings that were furnished, pursuant to Item 2.02 or Item 7.01 of Current Reports on Form 8-K (including exhibits related thereto) or other applicable SEC rules, rather than filed, prior to the consummation of the offering under this prospectus supplement:

If information in incorporated documents conflicts with information in this prospectus supplement you should rely on the most recent information. If information in an incorporated document conflicts with information in another incorporated document, you should rely on the most recent incorporated document.

Documents incorporated by reference are available from us without charge, excluding any exhibits to those documents unless the exhibit is specifically incorporated by reference as an exhibit in this document. You can obtain documents incorporated by reference in this document by requesting them in writing or by telephone at the following address and phone number:

ONEOK Partners, L.P.

Investor Relations Department

100 West Fifth Street

Tulsa, OK 74103-4298

(877) 208-7318 or (918) 588-7950

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PROSPECTUS

ONEOK PARTNERS, L.P.

COMMON UNITS REPRESENTING LIMITED PARTNER INTERESTS

DEBT SECURITIES

We may offer and sell, from time to time, common units representing limited partner interests or debt securities. The debt securities may be either senior or subordinated debt and may be fully and unconditionally guaranteed by ONEOK Partners Intermediate Limited Partnership. Additionally, the debt securities may be convertible into or exercisable or exchangeable for our common units.

We will provide the specific terms of the securities in supplements to this prospectus. Any prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and the accompanying prospectus supplement carefully before you make your investment decision. This prospectus may not be used to consummate sales of our securities unless it is accompanied by a prospectus supplement.

Our common units are listed for trading on the New York Stock Exchange under the symbol “OKS.”

We may sell securities to or through underwriters, dealers or agents. For additional information on the method of sale, you should refer to the section entitled “Plan of Distribution.” The names of any underwriters, dealers or agents involved in the sale of any securities and the specific manner in which they may be offered will be set forth in the prospectus supplement covering the sale of those securities.

Investing in these securities involves certain risks. Limited partnerships are inherently different from corporations. Please read “Risk Factors” on page 9 of this prospectus and in our most recently-filed Annual Report on Form 10-K and most recently-filed Quarterly Report on Form 10-Q and those that may be included in the applicable prospectus supplement and “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 4 of this prospectus and other information included and incorporated by reference in this prospectus for a discussion of the factors you should carefully consider before deciding to purchase these securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is September 15, 2009.

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ABOUT THIS PROSPECTUS

The information contained in this prospectus is not complete and may be changed. You should rely only on the information provided in or incorporated by reference in this prospectus, any prospectus supplement, or documents to which we otherwise refer you. We have not authorized anyone else to provide you with different information. We are not making an offer of any securities in any jurisdiction where the offer is not permitted. You should not assume that the information in this prospectus, any prospectus supplement or any document incorporated by reference is accurate as of any date other than the date of the document in which such information is contained or such other date referred to in such document, regardless of the time of any sale or issuance of a security.

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. Under this shelf process, we may sell different types of securities described in this prospectus in one or more offerings. This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering and the securities offered by us in that offering. The prospectus supplement may also add, update or change information in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described under the headings “Where You Can Find More Information” and “Incorporation by Reference.”

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by reference to the actual documents. Copies of some of the documents referred to herein have been filed or will be filed or incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described below in the section entitled “Where You Can Find More Information.”

Unless we otherwise indicate or unless the context requires, all references in this prospectus to “ONEOK Partners,” “we,” “us” and “our” or similar references mean ONEOK Partners, L.P. and its subsidiaries, predecessors and acquired businesses unless otherwise noted.

WHERE YOU CAN FIND MORE INFORMATION

We have filed a registration statement on Form S-3 with the SEC under the Securities Act of 1933, as amended, or the Securities Act, that registers the securities offered by this prospectus. The registration statement, including the attached exhibits, contains additional relevant information about us. The rules and regulations of the SEC allow us to omit some information included in the registration statement from this prospectus.

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You can read and copy any materials we file with the SEC at its Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You can obtain information about the operations of the SEC Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC also maintains a website that contains reports, proxy and information statements, and other information regarding issuers, including us, that file electronically with the SEC, which you can access over the Internet at http://www.sec.gov. General information about us, including our annual report on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, and amendments to those reports, is available free of charge at http://www.oneokpartners.com as soon as reasonably practicable after we electronically file them with, or furnish them to, the SEC. Information on our website is not incorporated into this prospectus or our other securities filings and is not a part of these filings. Our common units are listed on the New York Stock Exchange, or the NYSE, under the symbol “OKS,” and you can also obtain information about us at the offices of the NYSE, 20 Broad Street, New York, New York 10005.

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INCORPORATION BY REFERENCE

The SEC allows us to “incorporate by reference” information into this document. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will automatically update and supersede the previously filed information. We incorporate by reference the documents listed below and any future filings made by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act, other than any portions of the respective filings that were furnished, pursuant to Item 2.02 or Item 7.01 of Current Reports on Form 8-K (including exhibits related thereto) or other applicable SEC rules, rather than filed, prior to the termination of the offerings under this prospectus:

You may request a copy of these filings (other than an exhibit to the filings unless we have specifically incorporated that exhibit by reference into the filing), at no cost, by writing or telephoning us at the following address:

ONEOK Partners, L.P.

100 West Fifth Street

Tulsa, Oklahoma 74103

Attention: Corporate Secretary

Telephone: (918) 588-7000

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Some of the statements contained and incorporated in this prospectus are forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. The forward-looking statements relate to our anticipated financial performance, management’s plans and objectives for our future operations, our business prospects, the outcome of regulatory and legal proceedings, market conditions and other matters. We make these forward-looking statements in reliance on the safe harbor protections provided under the Private Securities Litigation Reform Act of 1995. The following discussion is intended to identify important factors that could cause future outcomes to differ materially from those set forth in the forward-looking statements.

Forward-looking statements include the items identified in the preceding paragraph, the information concerning possible or assumed future results of our operations and other statements contained or incorporated in this prospectus identified by words such as “anticipate,” “estimate,” “plan,” “expect,” “forecast,” “intend,” “believe,” “should,” “project,” “goal,” “could,” “may,” “continue,” “might,” “potential,” “scheduled” and other words and terms of similar meaning.

You should not place undue reliance on the forward-looking statements. Known and unknown risks, uncertainties and other factors may cause our actual results, performance or achievements to be materially

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different from any future results, performance or achievements expressed or implied by the forward-looking statements. Many of those factors that will determine these results are beyond our ability to control or predict. Those factors may affect our operations, markets, products, services and prices. In addition to any assumptions and other factors referred to specifically in connection with the forward-looking statements, factors that could cause our actual results to differ materially from those contemplated in any forward-looking statement include, among others, the following:

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These factors are not necessarily all of the important factors that could cause actual results to differ materially from those expressed in our forward-looking statements. Other factors could also have material adverse effects on our future results. These and other risks are described in greater detail under the caption “Risk Factors” on page 7 of this prospectus and in our most recent Annual Report on Form 10-K, and in our quarterly reports on Form 10-Q that are incorporated by reference and may be included in the applicable prospectus supplement. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by these factors. Other than as required under securities laws, we undertake no obligation to update publicly any forward-looking statement whether as a result of new information, subsequent events or change in circumstances, expectations or otherwise.

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ABOUT ONEOK PARTNERS, L.P.

We are a publicly-traded Delaware master limited partnership formed in 1993. Our common units are listed on the New York Stock Exchange under the trading symbol “OKS.” Our primary business objectives are to generate stable cash flow sufficient to pay quarterly cash distributions to our unitholders and to increase our quarterly cash distributions over time. We own and manage natural gas gathering, processing, storage and interstate and intrastate pipeline assets and one of the nation’s premier NGL systems, connecting much of the natural gas and NGL supply in the Mid-Continent region with key market centers. We also own a 50 percent interest in a leading transporter of natural gas imported from Canada into the United States. Our business operations are divided into the following four operating segments for U.S. generally accepted accounting principles segment reporting purposes, based on similarities in economic characteristics, products and services, types of customers, methods of distribution and regulatory environment:

We are managed by our sole general partner, ONEOK Partners GP, a Delaware limited liability company. Our general partner is managed by its sole member, ONEOK, Inc., an Oklahoma corporation.

Our principal executive offices are located at 100 West Fifth Street, Tulsa, Oklahoma 74103-4298, and our telephone number at that address is (918) 588-7000.

ONEOK PARTNERS INTERMEDIATE LIMITED PARTNERSHIP

ONEOK Partners Intermediate Limited Partnership, a Delaware limited partnership, is our wholly-owned subsidiary and is managed by its general partner, ONEOK ILP GP, L.L.C., a Delaware limited liability company and our direct, wholly-owned subsidiary. ONEOK Partners Intermediate Limited Partnership is a holding company through which we own our interests in our operating subsidiaries.

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RISK FACTORS

Limited partner interests are inherently different from the capital stock of a corporation, although many of the business risks to which we are subject are similar to those that would be faced by a corporation engaged in a similar business. Before you invest in our securities, you should carefully consider those risk factors included in our most recent annual report on Form 10-K and our quarterly reports on Form 10-Q that are incorporated herein by reference and those that may be included in the applicable prospectus supplement, together with all of the other information included in this prospectus, any prospectus supplement and the documents we incorporate by reference in evaluating an investment in our securities.

If any of the risks discussed in the foregoing documents were actually to occur, our business, financial condition, results of operations, or cash flow could be materially adversely affected. In that case, our ability to make distributions to our unitholders or pay interest on, or the principal of, any debt securities, may be reduced, the trading price of our securities could decline and you could lose all or part of your investment.

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USE OF PROCEEDS

We will use the net proceeds we receive from the sale of the securities offered by this prospectus for general partnership purposes unless we specify otherwise in an applicable prospectus supplement. These purposes may include repayment and refinancing of debt, working capital, capital expenditures and repurchases and redemptions of securities. We may invest any funds we do not require immediately for general partnership purposes in marketable securities and short-term investments.

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RATIO OF EARNINGS TO FIXED CHARGES

Our ratio of earnings to fixed charges in each of the periods shown is as follows:

For purposes of computing the ratio of earnings to fixed charges, “earnings” consists of pre-tax income from continuing operations before adjustment for income or loss from equity investees plus fixed charges and distributed income of equity investees, less interest capitalized. “Fixed charges” consist of interest charges capitalized and expensed, the amortization of debt discounts and issue costs and the representative interest portion of operating leases.

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DESCRIPTION OF COMMON UNITS REPRESENTING LIMITED PARTNER INTERESTS

The following is a brief description of our common and Class B units. Please read the description of our common units and Class B units, our partnership agreement and our cash distribution policy each as contained in Amendment No. 2 to our registration statement on Form 8-A filed on September 19, 2006 (including any amendment or report filed for the purpose of updating the description), which are incorporated herein by reference, for more information on the common units and Class B units, our partnership agreement and our cash distribution policy.

As of July 31, 2009, we had 59,912,777 common units and 36,494,126 Class B units outstanding, representing a 98% limited partner interest in us. Thus, our equity consists of a 2% general partner interest and common units and Class B units representing in the aggregate a 98% limited partner interest.

Cash Distributions

General

Rationale for our Cash Distribution Policy

Our cash distribution policy reflects a basic judgment that our unitholders will be better served by distributing our available cash rather than retaining it. Our available cash includes cash generated from the operation of our assets and businesses. Our cash distribution policy is consistent with the terms of the Partnership Agreement, which requires that we distribute all of our available cash on a quarterly basis. Because we are not subject to an entity-level federal income tax, we have more cash to distribute to you than would be the case if we were subject to such tax.

Limitations on Our Ability to Make Cash Distributions

There is no guarantee that unitholders will receive quarterly distributions from us. Our distribution policy may become subject to limitations and restrictions and may be changed at any time, including:

Our Cash Distribution Policy May Limit Our Ability to Grow

Because we distribute all of our available cash, our growth may not be as fast as businesses that reinvest their available cash to expand ongoing operations. We generally rely upon internal and external financing

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sources, including borrowings and issuances of debt and equity securities, to fund our acquisition and growth capital expenditures. However, to the extent we are unable to finance growth externally, our cash distribution policy may significantly impair our ability to grow.

Cash from Operations and Cash from Interim Capital Transactions

Overview

All cash distributed to unitholders will be characterized as either “cash from operations” or “cash from interim capital transactions.” We treat distributions of available cash constituting cash from operations differently than distributions of available cash constituting interim capital transactions.

Definition of Available Cash

Available cash generally means, for each calendar quarter ending prior to liquidation, all cash on hand at the end of the quarter:

Definition of Cash from Operations

Cash from operations means:

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all as determined on a consolidated basis. Where cash capital expenditures, or capital contributions by the Intermediate Partnership, are made in part in respect of capital additions and improvements and in part for other purposes, our general partner’s good faith allocation thereof between the portion made for capital additions and improvements and the portion made for other purposes shall be conclusive.

Notwithstanding the foregoing, cash from operations with respect to the calendar quarter in which the date of our liquidation occurs and any subsequent calendar quarter will equal zero.

Definition of Cash from Interim Capital Transactions

Cash from interim capital transactions generally means, at any date, the sum of the amounts of available cash as (i) are deemed to be cash from interim capital transactions pursuant to the Partnership Agreement and (ii) constitute distributions received prior to May 17, 2006 by the Intermediate Partnership from Northern Border Pipeline in respect of any transaction undertaken by Northern Border Pipeline that constitutes an interim capital transaction (as defined in the Partnership Agreement).

Characterization of Cash Distributions

We will treat all available cash distributed, regardless of its source, as coming from cash from operations until the sum of all available cash distributed since we began operations equals the cash from operations from the closing date of our initial public offering through the close of the immediately preceding calendar quarter. We will treat any amount distributed in excess of cash from operations, regardless of its source, as cash from interim capital transactions. We do not anticipate that we will make any distributions from cash from interim capital transactions.

Distributions of Available Cash Constituting Cash from Operations

Subject to the rights of the Class B unitholders contained in the Partnership Agreement, we will make distributions of available cash constituting cash from operations for any quarter in the following manner:

In the event that the minimum quarterly distribution or the first target distribution, the second target distribution and the third target distribution discussed below have been reduced to zero pursuant to the

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Partnership Agreement, the distribution of available cash constituting cash from operations with respect to any quarter will be made in accordance with the last bullet point under “—Incentive Distributions” below.

The preceding discussion is based on the assumptions that we do not issue additional classes of equity securities, other than the Class B units.

Incentive Distributions

Our general partner has the right to receive an increasing percentage of quarterly distributions of available cash constituting cash from operations after the minimum quarterly distribution and the target distribution levels described below have been achieved.

If for any quarter:

then, we will distribute any additional available cash constituting cash from operations for that quarter among the unitholders and our general partner in the following manner:

In each case, the amount of the target distribution set forth above is exclusive of any distributions to common unitholders to eliminate any cumulative arrearages in payment of the minimum quarterly distribution.

Distributions of Available Cash Constituting Cash from Interim Capital Transactions

How Distributions from Cash from Interim Capital Transactions Will Be Made

Unless otherwise required by the Partnership Agreement, we will make distributions of available cash constituting cash from interim capital transactions, if any, in the following manner:

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Effect of a Distribution from Cash from Interim Capital Transactions

The Partnership Agreement treats a distribution of cash from interim capital transactions as the repayment of the initial unit price from our initial public offering, which is a return of capital. The initial public offering price less any distributions of cash from interim capital transactions per unit is referred to as the “unrecovered initial unit price.” Each time a distribution of cash from interim capital transactions is made, the minimum quarterly distribution and the target distribution levels will be reduced proportionately to equal the product obtained by multiplying the otherwise applicable minimum quarterly distribution and the target distribution levels, as the case may be, by a fraction of which the numerator is the unrecovered initial unit price of the common units immediately after giving effect to such distribution and of which the denominator is the unrecovered initial unit price of the common units immediately prior to giving effect to such distribution. Because distributions of cash from interim capital transactions will reduce the minimum quarterly distribution, after any of these distributions are made it may be easier for our general partner to receive incentive distributions. However, any distribution of cash from interim capital transactions before the unrecovered initial unit price is reduced to zero cannot be applied to the payment of the minimum quarterly distribution or any arrearages.

Once we distribute cash from interim capital transactions on a unit issued in our initial public offering in an amount equal to the initial unit price, we will reduce the minimum quarterly distribution and the target distribution levels to zero. We will then make all future distributions from cash from operations, with 50% being paid to the holders of units and 50% to our general partner in respect of our general partner interest and the incentive distributions.

Adjustment to the Minimum Quarterly Distribution and Target Distribution Levels

In addition to adjusting the minimum quarterly distribution and target distribution levels to reflect a distribution of cash from interim capital transactions, if we combine our units into fewer units or subdivide our units into a greater number of units, we will proportionately adjust:

For example, if a two-for-one split of the common units should occur, the minimum quarterly distribution, the target distribution levels and the unrecovered initial unit price would each be reduced to 50% of its initial level and each Class B unit would be convertible into two common units. We will not make any adjustment by reason of the issuance of additional units for cash or property.

In addition, if legislation is enacted or if the interpretation of existing law is modified by a governmental taxing authority so that ONEOK Partners, the Intermediate Partnership, Northern Border Pipeline or any other subsidiary of ONEOK Partners becomes taxable as a corporation or otherwise subject to taxation as an entity for federal, state or local income tax purposes, the minimum quarterly distribution and the target distribution levels for each quarter, as the case may be, will be equal to the product obtained by multiplying (a) the amount thereof by (b) 1 minus the sum of (i) the highest marginal federal corporate (or other entity, as applicable) income tax rate of ONEOK Partners (directly or through its interest in any of its subsidiaries or Northern Border Pipeline) for the fiscal year of ONEOK Partners in which such quarter occurs (expressed as a percentage) plus (ii) the effective overall state and local income tax rate (expressed as a percentage) applicable to ONEOK Partners (directly or through its interest in any of its subsidiaries or Northern Border Pipeline) for the calendar year next preceding the calendar year in which such quarter occurs (after taking into account the benefit of any deduction allowable for federal income tax purposes with respect to the payment of state and local income taxes), but only to the extent of the increase in such rates resulting from such legislation or interpretation. To the extent that the actual tax liability differs from the estimated tax liability for any quarter, the difference will be accounted for in subsequent quarters.

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Distributions of Cash Upon Liquidation

Overview

If we dissolve in accordance with the Partnership Agreement, we will sell or otherwise dispose of our assets in a process called liquidation. We will first apply the proceeds of liquidation to the payment of our creditors. We will distribute any remaining proceeds to the unitholders and our general partner, in accordance with their capital account balances, as adjusted to reflect any gain or loss upon the sale or other disposition of our assets in liquidation.

The allocations of gain and loss upon liquidation are intended, to the extent possible, to entitle the holders of outstanding common units and the holders of outstanding Class B units to equal treatment upon our liquidation, to the extent required to permit such unitholders to receive their unrecovered initial unit price plus the minimum quarterly distribution for the quarter during which liquidation occurs. The common unitholders are then entitled to allocations to the extent of any unpaid arrearages in payment of the minimum quarterly distribution on the common units. After such allocations are made in respect of the common units, any additional gain is then allocated to the Class B units to the extent of any cumulative Class B unit arrearage, if any. However, there may not be sufficient gain upon our liquidation to enable the holders of common units or Class B units to fully recover all of these amounts, even though there may be cash available to pay distributions to the holders of Class B units. Any further net gain recognized upon liquidation will be allocated in a manner that takes into account the incentive distributions to our general partner.

Adjustments to Capital Accounts

We will make adjustments to capital accounts upon the issuance of additional units. In doing so, we will allocate any unrealized and, for tax purposes, unrecognized gain or loss resulting from the adjustments to the unitholders and our general partner in the same manner as we allocate gain or loss upon liquidation. In the event that we make positive adjustments to the capital accounts upon the issuance of additional units, we will allocate any later negative adjustments to the capital accounts resulting from the issuance of additional units or upon our liquidation in a manner which results, to the extent possible, in our general partner’s capital account balances equaling the amount which they would have been if no earlier positive adjustments to the capital accounts had been made.

Voting

Each holder of our common units is entitled to one vote for each common unit on all matters submitted to a vote of our unitholders; provided that, if at any time any person or group owns beneficially 20% or more of all common units, such common units so owned may not be voted on any matter and may not be considered to be outstanding when sending notices of a meeting of unitholders (unless otherwise required by law), calculating required votes, determining the presence of a quorum or for other similar purposes under our partnership agreement.

Class B Units

Our Class B units are entitled to the same distribution rights as the common units and generally have the same voting rights as our common units.

Effective April 7, 2007, the Class B limited partner units became entitled to receive increased quarterly distributions equal to 110 percent of the distributions paid with respect to our common units. However, on June 21, 2007, ONEOK, Inc., as the sole holder of our Class B limited partner units, waived its right to receive the increased quarterly distributions on the Class B units for the period of April 7, 2007, through December 31, 2007, and continuing thereafter until ONEOK, Inc. gives us no less than 90 days advance notice that it has withdrawn its waiver. Any such withdrawal of the waiver will be effective with respect to any distribution on the Class B units declared or paid on or after the 90 days following delivery of the notice.

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In addition, since the proposed amendments to our partnership agreement were not approved by the required two-thirds affirmative vote of our common unitholders, if our common unitholders vote at any time to remove ONEOK, Inc. or its affiliates as our general partner, quarterly distributions payable on the Class B limited partner units would increase to 123.5 percent of the distributions payable with respect to the common units, and distributions payable upon liquidation of the Class B limited partner units would increase to 123.5 percent of the distributions payable with respect to the common units.

Listing

Our outstanding common units are listed on the NYSE under the symbol “OKS.” We anticipate that any additional common units we issue will also be listed on the NYSE. Our outstanding Class B units are not listed on any national stock exchange, and we do not intend to so list the Class B units.

Transfer Agent and Registrar

Our transfer agent and registrar for the common units is Computershare Trust Company, N.A.

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DESCRIPTION OF DEBT SECURITIES

The following description sets forth the general terms and provisions that apply to the debt securities. Each prospectus supplement will state the particular terms that will apply to the debt securities included in the supplement. The debt securities will be either senior debt securities or subordinated debt securities issued by ONEOK Partners. If we offer senior debt securities, we will issue them under a senior indenture. If we offer subordinated debt securities, we will issue them under a subordinated indenture containing subordination provisions. The debt securities will be governed by the provisions of the applicable indenture and those made part of such indenture by reference to the Trust Indenture Act of 1939, as amended. We urge you to read the indentures filed as exhibits to the registration statement of which this prospectus is a part, because those indentures, and not this description, govern your rights as a holder of debt securities. For purposes of this “Description of the Debt Securities,” when we refer to “us,” “we,” “our,” “ours,” or “ONEOK Partners,” we are describing ourselves, ONEOK Partners, L.P. only, and not any of our subsidiaries. References in this prospectus to an “indenture” refer to each of the senior indenture and the subordinated indenture.

General

The Debt Securities

Any series of debt securities that we issue:

Neither indenture limits the aggregate principal amount of debt securities that we may issue under that indenture. We may issue debt securities under each indenture from time to time in separate series, up to the aggregate amount authorized for each such series.

We will prepare a prospectus supplement and either an indenture supplement or a resolution of the board of directors of our general partner and accompanying officers’ certificate relating to any series of debt securities that we offer, which will include specific terms relating to some or all of the following:

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This description of debt securities will be deemed modified, amended or supplemented by any description of any series of debt securities set forth in a prospectus supplement related to that series.

The prospectus supplement may also describe any material United States federal income tax consequences or other special considerations regarding the applicable series of debt securities, including those relating to:

At our option, we may make interest payments by check mailed to the registered holders of debt securities or, if so stated in the applicable prospectus supplement, at the option of a holder by wire transfer to an account designated by the holder.

Unless otherwise provided in the applicable prospectus supplement, fully registered securities may be transferred or exchanged at the office of the trustee at which its corporate trust business is principally administered in the United States, subject to the limitations provided in the indenture, without the payment of any service charge, other than any applicable tax or governmental charge.

Any funds we pay to a paying agent for the payment of amounts due on any debt securities that remain unclaimed for two years will be returned to us, and the holders of the debt securities must look only to us for payment after that time.

Ranking

The senior debt securities will have the same rank as all of our other unsecured and unsubordinated Debt. The subordinated debt securities will be subordinated to senior indebtedness as described under “Provisions Only in the Subordinated Indenture—Subordinated Debt Securities Subordinated to Senior Debt” below.

Guarantee

To the extent provided in a prospectus supplement and either an indenture supplement or a resolution of the board of directors of our general partner, in each case, relating to a particular series of debt securities, each of our Subsidiaries that becomes a guarantor of the debt securities of such series, and any of our Subsidiaries that is a successor thereto, will fully, irrevocably, unconditionally and absolutely guarantee the due and punctual payment of the principal of, and premium, if any, and interest on such debt securities, and all other amounts due and payable under the applicable indenture and such debt securities by ONEOK Partners to the trustee or the holders of such debt securities.

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No Limitation on Indebtedness

The indentures do not limit the amount of indebtedness or other obligations that we may incur and do not give you the right to require us to repurchase your debt securities upon a change of control.

Provisions Only in the Senior Indenture

Summary

The senior debt securities will rank equally in right of payment with all our other senior and unsubordinated Debt and senior in right of payment to any of our subordinated Debt (including the subordinated debt securities). The senior indenture will contain restrictive covenants, including provisions that:

We have described below these provisions. We have also set forth below the definitions of important terms used in these provisions.

Limitation on Liens

ONEOK Partners will not, and will not permit any Restricted Subsidiary to, create, incur, issue or assume any Debt secured by any Lien on any Principal Property, or on Capital Interests or Debt of any Restricted Subsidiary (“Restricted Securities”), without making effective provision for the outstanding debt securities under the indenture (except as otherwise specified pursuant to the indenture for the debt securities of any series) to be secured by the Lien equally and ratably with (or prior to) any and all Debt and obligations secured or to be secured thereby for so long as such Debt is so secured. The foregoing restriction will not apply to:

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Limitation on Sale-Leaseback Transactions

ONEOK Partners will not, and will not permit any Restricted Subsidiary to, enter into any Sale-Leaseback Transaction unless (i) ONEOK Partners or a Restricted Subsidiary would be entitled, without securing the outstanding debt securities under the indenture, to incur Debt secured by a Lien on the Principal Property that is

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the subject of such Sale-Leaseback Transaction; (ii) the Attributable Indebtedness associated therewith would be in an amount permitted under the last bullet point under “—Limitation on Liens” above; (iii) the proceeds received in respect of the Principal Property so sold and leased back at the time of entering into such Sale- Leaseback Transaction are used for the business and operations of ONEOK Partners or any of its Subsidiaries; or (iv) within 12 months after the sale or transfer, an amount equal to the proceeds received in respect of the Principal Property so sold and leased back at the time of entering into such Sale-Leaseback Transaction is applied to the prepayment (other than mandatory prepayment) of any outstanding debt securities under the indenture or Funded Debt of ONEOK Partners or a Restricted Subsidiary (other than Funded Debt that is held by ONEOK Partners or any Restricted Subsidiary or Funded Debt of ONEOK Partners that is subordinate in right of payment to any outstanding debt securities under the indenture).

Definitions

As used in the foregoing description of covenants by which we are bound pursuant to the senior indenture, the following terms have the following meanings:

“Attributable Indebtedness” means with respect to a Sale-Leaseback Transaction involving any Property, as of the time of determination, the least of (i) the fair market value of such Property (as determined in good faith by the Board of Directors); (ii) the present value of the total Net Amount of Rent required to be paid under the lease involved in such Sale-Leaseback Transaction during the remaining term thereof (including any renewal term exercisable at the lessee’s option or period for which the lease has been extended), discounted at the rate of interest set forth or implicit in the terms of such lease, compounded semiannually; and (iii) if the obligation with respect to such Sale-Leaseback Transaction constitutes an obligation that is required to be classified and accounted for as a Capital Lease Obligation for financial reporting purposes in accordance with U.S. generally accepted accounting principles, the amount equal to the capitalized amount of such obligation required to be paid by the lessee as determined in accordance with U.S. generally accepted accounting principles and included in the financial statements of the lessee.

“Capital Interests” of any person means any and all shares, interests, participations, rights or other equivalents (however designated) of capital stock of such person, including, without limitation, with respect to partnerships, partnership interests (whether general or limited), and with respect to limited liability companies, member interests and any other interest or participation that confers on the holder thereof the right to receive a share of the profits and losses of, or distributions of assets of, such person.

“Capital Lease Obligation” means, at the time any determination thereof is to be made, the amount of the liability in respect of a capital lease that would at such time be required to be capitalized on a balance sheet in accordance with U.S. generally accepted accounting principles.

“Consolidated Net Tangible Assets” means, at any date of determination, the aggregate amount of total assets included in the most recent quarterly or annual balance sheet of ONEOK Partners and its consolidated Subsidiaries prepared in accordance with U.S. generally accepted accounting principles less applicable reserves reflected in such balance sheet, after deducting the following amounts: (i) all current liabilities reflected in such balance sheet, provided, however, that there shall not be deducted billings recorded as revenues deferred pending the outcome of rate proceedings (less applicable income taxes thereon), if and to the extent the obligation to refund the same shall not have been finally determined; (ii) appropriate allowance for minority interests in Capital Interests of Subsidiaries; and (iii) all goodwill, trade names, trademarks, patents, unamortized debt discount and expenses and other like intangibles reflected in such balance sheet.

“Debt” means obligations for money borrowed, evidenced by notes, bonds, debentures or other similar evidences of borrowed money.

“Funded Debt” means all Debt maturing one year or more from the date of the incurrence, creation, assumption or guarantee thereof, all Debt directly or indirectly renewable or extendable, at the option of the

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debtor, by its terms or by the terms of any instrument or agreement relating thereto, to a date one year or more from the date of the incurrence, creation, assumption or guarantee thereof, and all Debt under a revolving credit or similar agreement obligating the lender or lenders to extend credit over a period of one year or more.

“Lien” means any lien, mortgage, pledge, encumbrance, charge or security interest securing Debt. However, the following types of transactions will not be considered to result in a Lien: (i) any acquisition by ONEOK Partners or any Restricted Subsidiary of any property or assets subject to any reservation or exception under the terms of which any vendor, lessor or assignor creates, reserves or excepts or has created, reserved or excepted an interest in oil, gas or any other mineral in place or the proceeds thereof, (ii) any conveyance or assignment whereby ONEOK Partners or any Restricted Subsidiary conveys or assigns to any Person or Persons an interest in oil, gas or any other mineral in place or the proceeds thereof, (iii) any Lien upon any property or assets either owned or leased by ONEOK Partners or any Restricted Subsidiary or in which ONEOK Partners or any Restricted Subsidiary owns an interest that secures for the benefit of the Person or Persons paying the expenses of developing or conducting operations for the recovery, storage, transportation or sale of the mineral resources of such property or assets (or property or assets with which it is unitized) the payment to such Person or Persons of ONEOK Partners’ or the Restricted Subsidiary’s proportionate part of such development or operating expenses or (iv) any hedging arrangements entered into in the ordinary course of business, including any obligation to deliver any mineral, commodity or asset in connection therewith.

“Net Amount of Rent” as to any lease for any period means the aggregate amount of rent payable by the lessee with respect to such period after excluding amounts, whether or not designated as rent or additional rent, required to be paid on account of or contingent upon maintenance and repairs, insurance, taxes, assessments, water rates and similar charges. In the case of any lease that is terminable by the lessee upon the payment of a penalty, such net amount shall be the lesser of (1) the net amount determined assuming termination of the lease on the first date such lease may be terminated (in which case such net amount shall also include the amount of such penalty, but no rent shall be considered as payable under such lease subsequent to the first date upon which it may be so terminated) and (2) such net amount assuming no such termination.

“Non-Recourse Debt” means, at any time, Debt incurred after the date of the indenture by ONEOK Partners or a Restricted Subsidiary in connection with the acquisition of property or assets by ONEOK Partners or a Restricted Subsidiary or the financing of the construction of or improvements on property, whenever acquired; provided that, under the terms of such Debt and pursuant to applicable law, the recourse at such time and thereafter of the lenders with respect to such Debt is limited to the property or assets so acquired, or such construction or improvements, including Debt as to which a performance or completion guarantee or similar undertaking was initially applicable to such Debt or the related property or assets if such guarantee or similar undertaking has been satisfied and is no longer in effect.

“Principal Property” means any property located in the United States, except any such property that in the opinion of the board of directors of the general partner of ONEOK Partners is not of material importance to the total business conducted by ONEOK Partners and its consolidated Subsidiaries.

“Property” means any right or interest of ONEOK Partners or any of its Subsidiaries in and to property of any kind whatsoever, whether real, personal or mixed and whether tangible or intangible.

“Restricted Subsidiary” means any Subsidiary that owns or leases a Principal Property.

“Sale-Leaseback Transaction” means any arrangement with any person pursuant to which ONEOK Partners or any of its Subsidiaries leases any Principal Property that has been or is to be sold or transferred by ONEOK Partners or its Subsidiaries to such person, other than (a) any such transaction involving a lease for a term of not more than three years or classified as an operating lease under U.S. generally accepted accounting principles, (b) any such transaction between ONEOK Partners and any of its Subsidiaries or between any Subsidiaries of ONEOK Partners, and (c) any such transaction executed by the time of, or within 12 months after the latest of,

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the acquisition, the completion of construction, development or improvement, or the commencement of commercial operation of ONEOK Partners’ Principal Property subject to such leasing transaction.

“Subsidiary” of any person means: