13D Filing: Coliseum Capital and Blue Bird Corp (BLBD)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE
13D/A

Under the Securities Exchange Act of 1934*

(Amendment No. 5)

Blue Bird
Corporation

(Name of Issuer)

Common Stock, par value $0.0001 per share (Common Shares)

(Title of Class of Securities)

095306106

(CUSIP Number)

Christopher Shackelton/Adam Gray

105 Rowayton Ave.

Rowayton, CT 06853

(Name,
Address and Telephone Number of PersonAuthorized to Receive Notices and Communications)

September 23, 2017

(Date of Event Which Requires Filing of this Statement)

If the filing person has
previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of sections 240.13d-1(e), 240.13d-1(f) or 140.13d-1(g), check the following box.  ☐

The information required on the remainder of this cover page shall not be
deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes).

CUSIP No. 095306106 (Common Stock)

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Explanatory Note: This Amendment No. 5 (this Amendment) to the Schedule 13D (the
Initial 13D) filed by the Filers (as defined below) with the U.S. Securities and Exchange Commission (the Commission) on March 10, 2015, as amended and supplemented by Amendment No. 1 to the Initial 13D filed on
February 16, 2017, Amendment No. 2 to the Initial 13D, filed on March 10, 2017, Amendment No. 3 to the Initial 13D, filed on March 22, 2017, and Amendment No. 4 to the Initial 13D, filed on June 20, 2017 amends and
supplements the items set forth herein.

As used in this statement, the term Filers collectively refers to:

Item 4. Purpose of Transaction.

Securities Purchase Agreement

CCP, CCP II, CSB, and
Blackwell Partners, LLC Series A, a Delaware limited liability company (the Separate Account and together with CCP, CCP II, and CSB, the Sellers and each, individually, a Seller) and Blue Bird Corporation,
a Delaware corporation (the Issuer), entered into a Securities Purchase Agreement (the Purchase Agreement) on September 23, 2017, pursuant to which the Sellers agreed to sell and the Issuer agreed to purchase all of
(i) the shares of common stock, par value $0.0001 (the Common Stock) of the Issuer, (ii) the shares of the Issuers 7.625% Series A Convertible Cumulative Preferred Stock, par value $0.0001 per share, and (iii) the
warrants to acquire Common Stock, in each case, owned by the Sellers (the Transaction Securities). The Issuer agreed to acquire the Transaction Securities for an aggregate purchase price of $32,113,843.36, reflecting a price per share of
Common Stock of $18.65. Pursuant to the Purchase Agreement, the Sellers will cause Mr. Adam Gray, a representative of the Sellers previously appointed to the board of directors of the Issuer, to resign from the board of the directors of the
Issuer, effective upon the closing of the transactions contemplated by the Purchase Agreement. A description of the Purchase Agreement contained herein is qualified in its entirety by reference to Exhibit 99.1, which is incorporated herein by
reference in its entirety.

Item 5. Interest in Securities of the Issuer.

Item 5 is amended and supplemented as follows:

As of the
date of this Amendment No. 5, the Filers own no securities of the Issuer. Pursuant to that certain Purchase Agreement entered into by and between CCP, CCP II, CSB, and the Separate Account and the Issuer as of September 23, 2017, the
Sellers sold all of their securities of the Issuer for a total sale price of $32,113,843.36. The information in Item 4 is incorporated herein by reference.

The information relating to the beneficial ownership of shares of common stock, $0.0001 par value per share (the Common Shares) of Blue Bird
Corporation (the Issuer) by each of the Filers set forth in Rows 7 through 13 of the cover pages hereto is incorporated herein by reference.

The information in Item 6 is incorporated herein by reference.

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Item 6. Contracts, Arrangement, Understandings or Relationships with Respect to Securities of the
Issuer.

CCM is an investment adviser whose clients, including CCP, CCP2 and the Separate Account, have the right to receive or the power to direct the
receipt of dividends from, or the proceeds from the sale of, the Common Shares, the Series A Shares and the Warrants. CC is the general partner of CCP and CCP2. Gray and Shackelton are the managers of CC and CCM. CCM may have the right to receive
performance-related fees from the Separate Account and CC may have the right to receive performance-related fees from CCP and CCP2.

Item 6 of the
Schedule 13D is hereby amended and supplemented. The information set forth in Item 4 of this Amendment is hereby incorporated by reference in this Item 6.

Item 7. Materials to be filed as Exhibits.

1.
Exhibit 99.1 Securities Purchase Agreement, dated September 23, 2017, by and between Coliseum Capital Partners, L.P., Coliseum Capital Partners II, L.P., Blackwell Partners, LLC Series A, and Coliseum School Bus Holdings, LLC and
Blue Bird Corporation.

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SIGNATURES

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

Dated: September 26, 2017

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EXHIBITS