Gallagher rejected his outright assignment to Triple-A Norfolk on Tuesday and elected free agency, Roch Kubatko of MASNSports.com reports.
Gallagher was claimed off waivers by the Orioles in September but won't remain with the organization through the offseason. He never saw the field in Baltimore but appeared in 18 games earlier in the year for Kansas City and went 9-for-42 with no home runs and five RBI.