UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT PURSUANT TO

SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported): August 26, 2016 (August 23, 2016)

MEMORIAL RESOURCE DEVELOPMENT CORP.

(Exact Name of Registrant as Specified in Charter)

Registrant’s telephone number, including area code: (713) 588-8300

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

In connection with the merger contemplated by the previously-disclosed Agreement and Plan of Merger, dated as of May 15, 2016, by and among Range Resources Corporation (“Range”), Memorial Resource Development Corp. (“MRD”), and Medina Merger Sub, Inc. (the “Merger”), on August 3, 2016, Range commenced offers to certain eligible holders (collectively, the “Eligible Holder Offers”) of the 5.875% Senior Notes due 2022 issued by MRD (the “Existing Notes”) to either (a) exchange any and all outstanding Existing Notes for up to $600 million aggregate principal amount of new senior notes issued by Range or (b) purchase for cash any and all outstanding Existing Notes. Range also commenced a concurrent cash offer (the “Concurrent Cash Tender Offer” and, together with the Eligible Holder Offers, the “Offers”) to those holders of the Existing Notes who are not Eligible Holders. Also, in connection with the Offers, Range solicited consents from noteholders to amend the indenture governing the Existing Notes (the “Existing Indenture”) to eliminate substantially all of the restrictive covenants and certain events of default applicable to the Existing Notes (collectively, the “Proposed Amendments”).

Based on the receipt of the requisite number of consents in the consent solicitations, on August 23, 2016, MRD and the respective guarantors under the Existing Notes executed a supplement to the Existing Indenture (the “Supplemental Indenture”) with respect to the Proposed Amendments. The Supplemental Indenture became effective upon execution, but will become operative only upon, among other things, consummation of the proposed Merger described above.

In addition, the Existing Indenture requires MRD to make an offer to repurchase the Existing Notes at 101% of their face amount, plus accrued and unpaid interest, upon the occurrence of a MRD “change of control” transaction, which would include the Merger. The Proposed Amendments amend the definition of “change of control” to exclude the Merger, as a result of which the repurchase requirement would not apply to the Merger.

The foregoing summary of the Supplemental Indenture does not purport to be complete and is qualified by reference to the full text of the Supplemental Indenture, which is filed herewith as Exhibit 4.1 hereto and incorporated by reference herein.

Important Additional Information

This Current Report on Form 8-K (“Form 8-K”) does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. This Form 8-K is being made in respect of transactions related to the proposed merger transaction involving Range and MRD.

In connection with the Merger, Range has filed with the Securities and Exchange Commission (the “SEC”) a registration statement on Form S-4 (333-211994) on June 13, 2016, as amended, which has been declared effective by the SEC and includes a joint proxy statement of Range and MRD and also constitutes a prospectus of Range. Each of Range and MRD also plan to file other relevant documents with the SEC regarding the Merger. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended. The definitive joint proxy statement/prospectus(es) for Range and/or MRD has been mailed to shareholders of Range and/or MRD, as applicable.

INVESTORS AND SECURITY HOLDERS OF RANGE AND MRD ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS REGARDING THE MERGER AND ANY OTHER RELEVANT DOCUMENTS FILED OR THAT MAY BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.

Investors and security holders may obtain free copies of the joint proxy statement/prospectus, any amendments or supplements thereto and other documents containing important information about Range and MRD, once such documents are filed with the SEC through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Range will be available free of charge on Range’s website at http://www.rangeresources.com under the heading “Investors” or by contacting Range’s Investor Relations Department by email at lsando@rangeresources.com, damend@rangeresources.com,

mfreeman@rangeresources.com, or by phone at 817-869-4267. Copies of the documents filed with the SEC by MRD will be available free of charge on MRD’s website at http://www.memorialrd.com under the heading “Investor Relations” or by phone at 713-588-8339.

Participants in the Solicitation

Range, MRD and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies in respect of the Merger. Information about the directors and executive officers of MRD is set forth in MRD’s proxy statement for its 2016 annual meeting of shareholders, which was filed with the SEC on April 1, 2016. Information about the directors and executive officers of Range is set forth in its proxy statement for its 2016 annual meeting of shareholders, which was filed with the SEC on April 8, 2016. These documents can be obtained free of charge from the sources indicated above.

Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the joint proxy statement/prospectus and other relevant materials to be filed with the SEC when such materials become available. Investors should read the joint proxy statement/prospectus carefully before making any voting or investment decisions regarding the Merger. You may obtain free copies of these documents from Range or MRD using the sources indicated above.

Cautionary Statement Regarding Forward-Looking Information

This Form 8-K contains certain “forward-looking statements” within the meaning of federal securities laws, including within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 that are not limited to historical facts, but reflect Range’s and MRD’s current beliefs, expectations or intentions regarding future events. Words such as “may,” “will,” “could,” “should,” “expect,” ““plan,” “project,” “intend,” “anticipate,” “believe,” “estimate,” “predict,” “potential,” “pursue,” “target,” “continue,” and similar expressions are intended to identify such forward-looking statements. The statements in this communication that are not historical statements, including statements regarding the expected timetable for completing the proposed transaction, benefits and synergies of the proposed transaction, costs and other anticipated financial impacts of the proposed transaction; the combined company’s plans, objectives, future opportunities for the combined company and products, future financial performance and operating results and any other statements regarding Range’s and MRD’s future expectations, beliefs, plans, objectives, financial conditions, assumptions or future events or performance that are not historical facts, are forward-looking statements within the meaning of the federal securities laws. These statements are subject to numerous risks and uncertainties, many of which are beyond Range’s or MRD’s control, which could cause actual results to differ materially from the results expressed or implied by the statements. These risks and uncertainties include, but are not limited to: failure to obtain the required votes of Range’s or MRD’s shareholders; the timing to consummate the proposed transaction; that the conditions to closing of the proposed transaction may not be satisfied or that the closing of the proposed transaction otherwise does not occur; the risk that a regulatory approval that may be required for the proposed transaction is not obtained or is obtained subject to conditions that are not anticipated; the diversion of management time on transaction-related issues; the ultimate timing, outcome and results of integrating the operations of Range and MRD; the effects of the business combination of Range and MRD, including the combined company’s future financial condition, results of operations, strategy and plans; potential adverse reactions or changes to business relationships resulting from the announcement or completion of the proposed transaction; expected synergies and other benefits from the proposed transaction and the ability of Range to realize such synergies and other benefits; expectations regarding regulatory approval of the transaction; the results of any merger-related litigation, settlements and investigations; actions by third parties, including governmental agencies; changes in the demand for or price of oil and/or natural gas can be significantly impacted by weakness in the worldwide economy; consequences of audits and investigations by government agencies and legislative bodies and related publicity and potential adverse proceedings by such agencies; compliance with environmental laws; changes in government regulations and regulatory requirements, particularly those related to oil and natural gas exploration; compliance with laws related to income taxes and assumptions regarding the generation of future taxable income; weather-related issues; changes in capital spending by customers; delays or failures by customers to make payments owed to us; impairment of oil and natural gas properties; structural changes in the oil and natural gas industry; and maintaining a highly skilled workforce.

Range’s and MRD’s respective reports on Form 10-K for the year ended December 31, 2015, Form 10-Q for the quarters ended March 31, 2016 and June 30, 2016, recent Current Reports on Form 8-K, and other SEC filings , including the registration statement on S-4, as amended, that includes a joint proxy statement of Range and MRD and constitutes a prospectus of Range, discuss some of the important risk factors identified that may affect these factors and Range’s and MRD’s respective business, results of operations and financial condition. Range and MRD undertake no obligation to revise or update publicly any forward-looking statements for any reason. Readers are cautioned not to place undue reliance on these forward-looking statements that speak only as of the date hereof.

SIGNATURES

Pursuant to the requirements of the Exchange Act, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Exhibit Index