Exhibit 5.1

Opinion of Latham & Watkins LLP

February 27, 2012

QEP Resources, Inc.

1050 17th Street, Suite 500

Denver, Colorado 80265

Re: QEP Resources, Inc. Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as special counsel to QEP Resources, Inc., a Delaware corporation (the “Company”), in connection with its filing on February 27, 2012 with the Securities and Exchange Commission (the “Commission”) of a registration statement on Form S-3 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Act”), relating to the registration for issue and sale by the Company from time to time of one or more series of debt securities of the Company (the “Debt Securities”), shares of common stock of the Company, par value $0.01 per share (the “Common Stock”), or any combination of the foregoing (collectively, the “Securities”) having an indeterminate aggregate initial offering price. The Securities shall include any additional amounts of such securities registered by the Company pursuant to Rule 462(b) under the Act in connection with the offering contemplated by the Registration Statement. The Debt Securities will be issued pursuant to a senior indenture to be entered into between the Company and Wells Fargo Bank, National Association, as trustee, a form of which is attached as Exhibit 4.1 to the Registration Statement, and one or more officer’s certificates or supplemental indentures thereto (the “Indenture”). You have provided us with a draft of the Registration Statement in the form in which it will be filed, which includes a form of prospectus (the “Prospectus”). The Prospectus provides that it will be supplemented in the future by one or more supplements to the Prospectus (each, a “Prospectus Supplement”). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement, the Prospectus or any Prospectus Supplement, other than as expressly stated herein with respect to the issue of the Securities.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the internal laws of the State of New York, and in numbered paragraph 1 of this letter, the Delaware General Corporation Law, and we express no opinion with respect to the applicability thereto, or the effect thereon, of the laws of any other jurisdiction or, in the case of Delaware, any other laws, or as to any matters of municipal law or the laws of any local agencies within any state.

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Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof:

(1) When an issuance of Common Stock has been duly authorized by all necessary corporate action of the Company, upon issuance, delivery and payment therefor in an amount not less than the par value thereof, in the manner contemplated by the Registration Statement, the Prospectus and the applicable Prospectus Supplement(s) and by such corporate action, such shares of Common Stock will be validly issued, fully paid and nonassesable.

(2) When the Indenture has been duly authorized by all necessary corporate action of the Company and duly executed and delivered, and when the specific terms of a particular Debt Security have been duly established in accordance with such Indenture and authorized by all necessary corporate action of the Company, and such Debt Security has been duly executed, authenticated, issued and delivered against payment therefor in accordance with such Indenture and in the manner contemplated by the Registration Statement, the Prospectus and the applicable Prospectus Supplement(s) and by such corporate action, such Debt Security will be a legally valid and binding obligation of the Company, enforceable against the Company in accordance with its terms.

Our opinions are subject to: (i) the effect of bankruptcy, insolvency, reorganization, preference, fraudulent transfer, moratorium or other similar laws relating to or affecting the rights and remedies of creditors; (ii) the effect of general principles of equity, whether considered in a proceeding in equity or at law (including the possible unavailability of specific performance or injunctive relief), concepts of materiality, reasonableness, good faith and fair dealing, and the discretion of the court before which a proceeding is brought; and (iii) the invalidity under certain circumstances under law or court decisions of provisions providing for the indemnification of or contribution to a party with respect to a liability where such indemnification or contribution is contrary to public policy. We express no opinion as to (a) any provision for liquidated damages, default interest, late charges, monetary penalties, make-whole premiums or other economic remedies to the extent such provisions are deemed to constitute a penalty, (b) consents to, or restrictions upon, governing law, jurisdiction, venue, arbitration, remedies or judicial relief, (c) waivers of rights or defenses, (d) any provision requiring the payment of attorneys’ fees, where such payment is contrary to law or public policy, (e) any provision permitting, upon acceleration of any Debt Security, collection of that portion of the stated principal amount thereof which might be determined to constitute unearned interest thereon, (f) the creation, validity, attachment, perfection, or priority of any lien or security interest, (g) advance waivers of claims, defenses, rights granted by law, or notice, opportunity for hearing, evidentiary requirements, statutes of limitation, trial by jury or at law, or other procedural rights, (h) waivers of broadly or vaguely stated rights, (i) provisions for exclusivity, election or cumulation of rights or remedies, (j) provisions authorizing or validating conclusive or discretionary determinations, (k) grants of setoff rights, (1) proxies, powers and trusts, (m) provisions prohibiting, restricting, or requiring consent to assignment or transfer of any right or property, (n) provisions purporting to make a guarantor primarily liable rather than as a surety, (o) provisions purporting to waive modifications of any guaranteed obligation to the extent such

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modification constitutes a novation, (p) any provision to the extent it requires that a claim with respect to a security denominated in other than U.S. dollars (or a judgment in respect of such a claim) be converted into U.S. dollars at a rate of exchange at a particular date, to the extent applicable law otherwise provides, and (q) the severability, if invalid, of provisions to the foregoing effect.

With your consent, we have assumed (i) that each of the Debt Securities and the Indenture (collectively, the “Documents”) will be governed by the internal laws of the State of New York, (ii) that each of the Documents will be duly authorized, executed and delivered by the parties thereto, (iii) that each of the Documents will constitute legally valid and binding obligations of the parties thereto other than the Company, enforceable against each of them in accordance with their respective terms and (iv) that the status of each of the Documents as legally valid and binding obligations of the parties will not be affected by any (a) breaches of, or defaults under, agreements or instruments, (b) violations of statutes, rules, regulations or court or governmental orders, or (c) failures to obtain required consents, approvals or authorizations from, or to make required registrations, declarations or filings with, governmental authorities.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Registration Statement and to the reference to our firm contained in the Prospectus under the heading “Legal Matters.” We further consent to the incorporation by reference of this letter and consent into any registration statement or post-effective amendment to the Registration Statement filed pursuant to Rule 462(b) with respect to the Securities. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ LATHAM & WATKINS LLP