Hart was optioned to Double-A Bowie on Sunday, Roch Kubatko of MASN Sports reports.
As the low man in the pecking order of the Orioles' bullpen, Hart was sent out when the team needed to clear a roster spot for Darren O'Day (hamstring), who will return from the DL following a nearly two-month absence. Hart made three scoreless appearances with the Orioles in his first stint in the big leagues, covering 2.2 innings.