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): July 8, 2015

EAGLE ROCK ENERGY PARTNERS, L.P.

(Exact name of Registrant as specified in its charter)

1415 Louisiana Street, Suite 2700

Houston, Texas 77002

(Address of principal executive offices, including zip code)

(281) 408-1200

(Registrant’s telephone number, including area code)

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:

x   Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o   Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o   Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o   Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 7.01. Regulation FD Disclosure.

On July 8, 2015, Eagle Rock Energy Partners, L.P. (the “Partnership”) issued a press release announcing it has established a record date of close of business on August 6, 2015 and a meeting date of September 17, 2015 for the special meeting of the Partnership’s unitholders to consider and vote upon a proposal to approve and adopt the previously announced Agreement and Plan of Merger, dated as of May 21, 2015, by and among the Partnership, Eagle Rock Energy GP, L.P., the general partner of the Partnership, Vanguard Natural Resources, LLC (“Vanguard”), and Talon Merger Sub, LLC, a newly formed, wholly owned indirect subsidiary of Vanguard (“Merger Sub”) and other related matters (the “Special Meeting”). Unitholders of record at the close of business on August 6, 2015 will be entitled to receive notice of the Special Meeting and to vote at the Special Meeting. A copy of the press release announcing the record date and meeting date for the Special Meeting is attached as Exhibit 99.1 hereto and incorporated by reference herein.

Item 8.01. Other Events.

The information included in Item 7.01 of this Current Report on Form 8-K is incorporated by reference into this Item 8.01 of this Current Report on Form 8-K.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

99.1 Press release of Eagle Rock Energy Partners, L.P. dated July 8, 2015

Additional Information about the Proposed Transactions

This communication 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. In connection with the proposed merger, Vanguard has filed with the Securities and Exchange Commission (the “SEC”) a preliminary Registration Statement on Form S-4 that includes a preliminary joint proxy statement of the Partnership and Vanguard that also constitutes a preliminary prospectus of Vanguard. After the registration statement has been declared effective by the SEC, a definitive joint proxy statement/prospectus will be sent to (i) security holders of Eagle Rock seeking their approval with respect to the proposed merger and (ii) security holders of Vanguard seeking their approval with respect to the issuance of Vanguard common units in connection with the proposed merger. Vanguard and Eagle Rock also have filed and may file other documents with the SEC regarding the proposed transaction. INVESTORS AND SECURITY HOLDERS ARE URGED TO CAREFULLY READ THE JOINT PROXY STATEMENT/PROSPECTUS (INCLUDING ALL AMENDMENTS AND SUPPLEMENTS THERETO) AND OTHER DOCUMENTS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. Investors and security holders will be able to obtain a free copy of the joint proxy statement/prospectus (if and when it becomes available) and other documents, once such documents are filed by Vanguard and Eagle Rock with the SEC, through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Vanguard will be available free of charge on Vanguard’s internet website at http://www.vnrllc.com or by contacting Vanguard’s Investor Relations Department by email at investorrelations@vnrllc.com or by phone at (832) 327-2234. Copies of the documents filed with the SEC by Eagle Rock will be available free of charge on Eagle Rock’s internet website at http://www.eaglerockenergy.com or by contacting Eagle Rock’s Investor Relations Department by email at info@eaglerockenergy.com or by phone at (281) 408-1203.

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Participants in the Solicitation

Vanguard, Eagle Rock, and their respective directors, executive officers and other members of their management and employees may be deemed to be “participants” in the solicitation of proxies in connection with the proposed merger. Investors and security holders may obtain information regarding Vanguard’s directors, executive officers and other members of its management and employees in Vanguard’s Annual Report on Form 10-K for the year ended December 31, 2014, which was filed with the SEC on March 2, 2015, Vanguard’s proxy statement for its 2015 annual meeting, which was filed with the SEC on April 20, 2015, and any subsequent statements of changes in beneficial ownership on file with the SEC. Investors and security holders may obtain information regarding Eagle Rock’s directors, executive officers and other members of their management and employees in Eagle Rock’s Annual Report on Form 10-K for the year ended December 31, 2014, which was filed with the SEC on March 2, 2015, Eagle Rock’s proxy statement for its annual meeting, which was filed with the SEC on March 31, 2015 and any subsequent statements of changes in beneficial ownership on file with the SEC. These documents can be obtained free of charge from the sources listed above. Additional information regarding the direct and indirect interests of these individuals will also be included in the joint proxy statement/prospectus regarding the proposed transaction when it becomes available.

Cautionary Statement Regarding Forward-Looking Information

This communication includes “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933. All statements other than historical facts, including, without limitation, statements regarding the expected benefits of the proposed transaction to Vanguard and Eagle Rock and their unitholders, the anticipated completion of the proposed transaction or the timing thereof, the expected future reserves, production, financial position, business strategy, revenues, earnings, costs, capital expenditures and debt levels of the combined company, and plans and objectives of management for future operations, are forward-looking statements. When used in this press release, words such as we “may,” “can,” “expect,” “intend,” “plan,” “estimate,” “anticipate,” “predict,” “project,” “foresee,” “believe,” “will” or “should,” “would,” “could,” or the negative thereof or variations thereon or similar terminology are generally intended to identify forward-looking statements. It is uncertain whether the events anticipated will transpire, or if they do occur what impact they will have on the results of operations and financial condition of Vanguard, Eagle Rock or of the combined company. Such forward-looking statements are subject to risks and uncertainties that could cause actual results to differ materially from those expressed in, or implied by, such statements. These risks and uncertainties include, but are not limited to: the ability to obtain unitholder approval of the proposed transaction; the ability to complete the proposed transaction on anticipated terms and timetable; Vanguard’s and Eagle Rock’s ability to integrate successfully after the transaction and achieve anticipated benefits from the proposed transaction; the possibility that various closing conditions for the transaction may not be satisfied or waived; risks relating to any unforeseen liabilities of Vanguard or Eagle Rock; declines in oil, NGL or natural gas prices; the level of success in exploitation, development and production activities; adverse weather conditions that may negatively impact development or production activities; the timing of exploitation and development expenditures; inaccuracies of reserve estimates or assumptions underlying them; revisions to reserve estimates as a result of changes in commodity prices; impacts to financial statements as a result of impairment write-downs; risks related to level of indebtedness and periodic redeterminations of the borrowing base under Vanguard’s and Eagle Rock’s credit agreements; the ability of Vanguard and Eagle Rock to comply with covenants contained in the agreements governing their indebtedness; ability to generate sufficient cash flows from operations to meet the internally funded portion of any capital expenditures budget; ability to obtain external capital to finance exploitation and development operations and acquisitions; federal, state and local initiatives and efforts relating to the regulation of hydraulic fracturing; failure of properties to yield oil or gas in commercially viable quantities; uninsured or underinsured losses resulting from oil and gas operations; inability to access oil and gas markets due to market conditions or operational impediments; the impact and costs of compliance with laws and regulations governing oil and gas operations; ability to replace oil and natural gas reserves; any loss of senior management or technical personnel; competition in the oil and gas industry; risks arising out of hedging transactions. Eagle Rock and Vanguard caution that the foregoing list of factors is not exclusive. Additional information concerning these and other risk factors are contained in Eagle Rock’s and Vanguard’s Annual Reports on Form 10-K for the period ended December 31, 2014, subsequent Quarterly Reports on Form 10-Q, recent Current Reports on Form 8-K, and other SEC filings, which are available at the SEC’s website, http://www.sec.gov. Readers are cautioned not to place undue reliance on forward-looking statements, which speak only as of their dates. Except as required by law, neither Vanguard nor Eagle Rock intends to update or revise its forward-looking statements, whether as a result of new information, future events or otherwise.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Partnership has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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Exhibit Index

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