SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b), (c)

AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Spirit Realty Capital, Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

84860F109

(CUSIP Number)

December 31, 2012

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

x Rule 13d-1(b)

¨ Rule 13d-1(c)

¨ Rule 13d-1(d)

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SCHEDULE 13G

This Schedule 13G (this “Schedule 13G”) is being filed on behalf of Granite Bay Advisors, L.P., a Delaware limited partnership (“Granite Bay”), Granite Bay Advisors GP, LLC, a Delaware limited liability company (“Granite Bay GP”), NexPoint Credit Strategies Fund, a Delaware statutory trust (the “Credit Fund”), NexPoint Advisors, L.P., a Delaware limited partnership (“NexPoint”), NexPoint Advisors GP, LLC, a Delaware limited liability company (“NexPoint GP”), Pyxis Floating Rate Opportunities Fund, a series of Pyxis Funds I, a Delaware statutory trust (the “Floating Rate Fund”), Pyxis Capital, L.P., a Delaware limited partnership (“Pyxis”), Strand XVI, Inc., a Delaware corporation (“Strand XVI”), Highland Capital Management, L.P., a Delaware limited partnership (“Highland Capital”), Strand Advisors, Inc., a Delaware corporation (“Strand”), and James D. Dondero (collectively, the “Reporting Persons”).

Mark Okada is the President of Granite Bay GP, Brad Ross is the President of Strand XVI and James D. Dondero is the President of NexPoint GP and Strand. Granite Bay GP is the general partner of Granite Bay. Granite Bay serves as the investment advisor to certain private funds (the “Granite Bay Funds”). NexPoint GP is the general partner of NexPoint. NexPoint serves as the investment advisor to the Credit Fund. Strand XVI is the general partner of Pyxis. Pyxis is the investment advisor to the Floating Rate Fund. Strand is the general partner of Highland Capital. Highland Capital serves as the advisor to certain private funds and managed accounts (the “Private Funds” and collectively with the Granite Bay Funds, the Credit Fund and the Floating Rate Fund, the “Funds”). This Schedule 13G relates to shares of Common Stock, par value $0.01 per share (the “Common Stock”), of Spirit Realty Capital, Inc., a Maryland corporation (the “Issuer”), held by the Funds.

Spirit Realty Capital, Inc.

16767 North Perimeter Drive

Suite 210

Scottsdale, Arizona 85260

(1) Granite Bay Advisors, L.P.

(2) Granite Bay Advisors GP, LLC

(3) NexPoint Credit Strategies Fund

(4) NexPoint Advisors, L.P.

(5) NexPoint Advisors GP, LLC

(6) Pyxis Floating Rate Opportunities Fund

(7) Pyxis Capital, L.P.

(8) Strand XVI, Inc.

(9) Highland Capital Management, L.P.

(10) Strand Advisors, Inc.

(11) James D. Dondero

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For all Filers:

300 Crescent Court, Suite 700

Dallas, Texas 75201

(1) Granite Bay Advisors, L.P. is a Delaware limited partnership

(2) Granite Bay Advisors GP, LLC is a Delaware limited liability company

(3) NexPoint Credit Strategies Fund is a Delaware statutory trust

(4) NexPoint Advisors, L.P. is a Delaware limited partnership

(5) NexPoint Advisors GP, LLC is a Delaware limited liability company

(6) Pyxis Floating Rate Opportunities Fund is a series of a Delaware statutory trust

(7) Pyxis Capital, L.P. is a Delaware limited partnership

(8) Strand XVI, Inc. is a Delaware corporation

(9) Highland Capital Management, L.P. is a Delaware limited partnership

(10) Strand Advisors, Inc. is a Delaware corporation

(11) James D. Dondero is a United States citizen

Common Stock, par value $0.01 per share.

84860F109

If this statement is filed pursuant to Rule 13d-1(b), or 13d-2(b), check whether the person filing is a:

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The Credit Fund is the beneficial owner of 260,625 shares of Common Stock that it holds directly. NexPoint, as the investment advisor to the Credit Fund, and NexPoint GP, as the general partner of NexPoint, may be deemed the beneficial owners of the 260,625 shares of Common Stock held by the Credit Fund.

The Floating Rate Fund is the beneficial owner of 578,225 shares of Common Stock that it holds directly. Pyxis, as the investment advisor to the Floating Rate Fund, and Pyxis GP, as the general partner of Pyxis, may be deemed the beneficial owners of the 578,225 shares of Common Stock held by the Floating Rate Fund.

Highland Capital, as the investment advisor to the Private Funds, and Strand, as the general partner of Highland Capital, may be deemed the beneficial owners of the 3,436,534 Common Shares held by the Private Funds.

Mr. Dondero may be deemed the beneficial owner of the 4,385,584 Common Shares held by the Funds.

The Credit Fund, NexPoint and NexPoint GP may be deemed the beneficial owners of 0.3% of the outstanding shares of Common Stock held by the Credit Fund.

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The Floating Rate Fund, Pyxis and Pyxis GP may be deemed the beneficial owners of 0.7% of the outstanding shares of Common Stock held by the Floating Rate Fund.

Highland Capital and Strand may be deemed the beneficial owners of 4.1% of the outstanding shares of Common Stock held by the Private Funds.

Mr. Dondero may be deemed the beneficial owner of 5.2% of the outstanding shares of Common Stock held by the Funds.

The above percentages were determined by dividing the number of shares of Common Stock held by each of the Reporting Persons, respectively, by 84,851,515, which is the number of Common Shares outstanding as of November 6, 2012 according to the Issuer’s Form 10-Q filed with the Securities and Exchange Commission on November 8, 2012.

The Credit Fund has the sole power to vote and dispose of the 260,625 shares of Common Stock that it holds directly. NexPoint and NexPoint GP have the shared power to vote and dispose of the 260,625 shares of Common Stock held by the Credit Fund.

The Floating Rate Fund has the sole power to vote and dispose of the 578,225 shares of Common Stock that it holds directly. Pyxis and Pyxis GP have the shared power to vote and dispose of the 578,225 shares of Common Stock held by the Credit Fund.

Highland Capital and Strand have the shared power to vote and dispose of the 3,436,534 shares of Common Stock held by the Private Funds.

Mr. Dondero has the shared power to vote and dispose of the 4,385,584 shares of Common Stock held by the Funds.

Inapplicable.

As discussed above, Highland Capital may be deemed the beneficial owner of shares of Common Stock held by certain managed accounts that are not Reporting Persons for purposes of this Schedule 13G.

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Inapplicable.

Inapplicable.

Inapplicable.

By signing below each of the Reporting Persons certifies that, to the best of such person’s knowledge and belief, the securities referred to above were acquired and held in the ordinary course of business and were not acquired and were not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Joint Filing Agreement, dated February 13, 2013, by and among Granite Bay Advisors, L.P., Granite Bay Advisors GP, LLC, NexPoint Credit Strategies Fund, NexPoint Advisors, L.P., NexPoint Advisors GP, LLC, Pyxis Floating Rate Opportunities Fund, Pyxis Capital, L.P., Strand XVI, Inc., Highland Capital Management, L.P., Strand Advisors, Inc. and James D. Dondero.

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 13, 2013

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Exhibit 99.1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto) with respect to the Common Stock, par value $0.01 per share, of Spirit Realty Capital, Inc., and further agree that this Joint Filing Agreement shall be included as an Exhibit to such joint filings.

The undersigned further agree that each party hereto is responsible for the timely filing of such Statement on Schedule 13G and any amendments thereto, and for the accuracy and completeness of the information concerning such party contained therein; provided, however, that no party is responsible for the accuracy or completeness of the information concerning any other party, unless such party knows or has reason to believe that such information is inaccurate.

This Joint Filing Agreement may be signed in counterparts with the same effect as if the signature on each counterpart were upon the same instrument.

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IN WITNESS WHEREOF, the undersigned have executed this Agreement as of February 13, 2013.