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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ( Mark One ) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM ΤΟ Oak Street Health , Inc. ( Exact name of Registrant as specified in its Charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 30 W. Monroe Street , Suite 1200 Chicago , Illinois 60603 ( Address of principal executive offices ) Commission File Number 001-39427 Securities registered pursuant to Section 12 ( b ) of the Act : Registrant's telephone number , including area code : ( 312 ) 733-9730 Trading Symbol ( s ) OSH 84-3446686 ( I.R.S. Employer Identification No. ) 60603 ( Zip Code ) Name of each exchange on which registered NYSE Title of each class Common Stock , $ 0.001 per share par value Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the Registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . YES NO Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . YES NO > Indicate by check mark whether the Registrant : ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the Registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . YES NO Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the Registrant was required to submit such files ) . YES NO Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , smaller reporting company , or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer || Accelerated filer Non - accelerated filer Smaller reporting company □ Emerging growth company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . O DOCUMENTS INCORPORATED BY REFERENCE Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . □ Indicate by check mark whether the Registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . YES NO > The registrant was not a public company as of the last business day of its most recently completed second fiscal quarter and therefore , cannot calculate the aggregate market value of its common stock held by non - affiliates as of such date . The number of shares of Registrant's Common Stock outstanding as of March 4 , 2021 was 240,747,470 . List hereunder the following documents if incorporated by reference and the Part of the Form 10 - K ( e.g. , Part I , Part II , etc. ) into which the document is incorporated : ( 1 ) Any annual report to security holders ; ( 2 ) Any proxy or information statement ; and ( 3 ) Any prospectus filed pursuant to Rule 424 ( b ) or ( c ) under the Securities Act of 1933. The listed documents should be clearly described for identification purposes ( e.g. , annual report to security holders for fiscal year ended December 24 , 1980 )