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 2, 2013

O’REILLY AUTOMOTIVE, INC.

(Exact Name of Registrant as Specified in its Charter)

233 South Patterson

Springfield, Missouri 65802

(Address of principal executive offices, Zip code)

(417) 862-6708

(Registrant’s telephone number, including area code)

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:

Credit Agreement and Guaranty Amendment

On July 2, 2013 (the “Amendment Date”), O’Reilly Automotive, Inc. (the “Company”) entered into Amendment No. 2 to Credit Agreement and Amendment No. 1 to Guaranty with Bank of America, N.A., as Administrative Agent, L/C Issuer, Swing Line Lender and a Lender, and the other lenders party thereto (the “Amendment”), which amends (i) the Credit Agreement dated as of January 14, 2011, by and among the Company, Bank of America, N.A., as Administrative Agent, Swing Line Lender, L/C Issuer and a Lender, and the other lenders party thereto (as amended by Amendment No. 1 to Credit Agreement dated as of September 9, 2011, and as further amended by the Amendment, the “Credit Agreement”) and (ii) the Guaranty Agreement dated as of January 14, 2011 (as amended by the Amendment, the “Guaranty”) by and among the guarantors party thereto and the Administrative Agent.

In connection with the Amendment, the aggregate commitments have been reduced and now consist of $600 million senior unsecured revolving credit commitments, with a $200 million sub-limit for the issuance of letters of credit and a $75 million sub-limit for swing line borrowings. The Credit Agreement also provides for an uncommitted incremental facility that permits the Company, subject to certain conditions, to increase the commitments under the new senior unsecured revolving credit facility by up to $200 million.

The Amendment provides for, among other things, an extension of the maturity date of the credit facility to July 2, 2018, and a decrease in the interest rate margins applicable to loans made under the Credit Agreement and the facility fee paid on the amount of the commitments thereunder. Loans made under the Credit Agreement (other than swing line loans) will now bear interest, at the Company’s option, at either a Base Rate (as set forth in the Credit Agreement) or a Eurodollar Rate (as set forth in the Credit Agreement) plus a margin that will vary from 0.000% to 0.250% in the case of Base Rate loans and 0.875% to 1.250% in the case of Eurodollar Rate loans, in each case, based upon the better of the ratings assigned to the Company’s debt by Moody’s Investors Service, Inc. and Standard & Poor’s Ratings Services. Borrowings of swing line loans under the Credit Agreement bear interest at a Base Rate plus the margin described above for Base Rate loans. In addition, under the terms of the Credit Agreement, the Company pays a facility fee on the aggregate amount of the commitments in an amount equal to a percentage of such commitments. That percentage has been reduced pursuant to the Amendment and will now vary from 0.125% to 0.250% based upon the better of the ratings assigned to the Company’s debt by Moody’s Investors Service, Inc. and Standard & Poor’s Ratings Services.

Pursuant to the Guaranty, the Company’s obligations under the Credit Agreement are guaranteed by its subsidiaries, other than foreign subsidiaries to the extent adverse tax consequences would result from such guaranty and certain immaterial subsidiaries. As of the Amendment Date, all of the Company’s subsidiaries, other than immaterial subsidiaries, are guarantors under the Credit Agreement.

The Amendment does not change the covenants or events of default applicable to the Company and its subsidiaries.

As of the date of the Amendment, there were no outstanding borrowings under the credit facility.

In addition to the specific agreements and arrangements described above, affiliates of some of the parties to the Credit Agreement and their respective affiliates have provided and may in the future provide certain financial advisory, investment banking and commercial banking services in the ordinary course of business for the Company, its subsidiaries and certain of their respective affiliates, for which they have received or will receive customary fees and expenses in connection with the performance of such services.

The foregoing description of the terms of the Credit Agreement, the Guaranty and the Amendment does not purport to be complete and is qualified in its entirety by reference to (i) the Credit Agreement, attached as Exhibit 10.1 to the Company’s Form 8-K filing dated January 11, 2011, and incorporated herein by reference, (ii) Amendment No. 1 to Credit Agreement, attached as Exhibit 10.1 to the Company’s Form 8-K filing dated September 9, 2011, and incorporated herein by reference, (iii) the Guaranty, attached as part of Exhibit 10.1 to the Company’s Form 8-K filing dated January 11, 2011, and incorporated herein by reference, and (iv) the Amendment, attached as Exhibit 10.1 hereto, and incorporated herein by reference.

(d) Exhibits:

SIGNATURES

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

Date: July 3, 2013

EXHIBIT INDEX