Hart was recalled from Triple-A Norfolk on Tuesday, Roch Kubatko of MASN Sports reports.
Hart was optioned to Norfolk on Monday, but the Orioles brought him back just one day later as an injury replacement for Dylan Bundy (ankle), who landed on the disabled list. Hart had a 1.35 ERA at the big-league level this year before giving up two earned runs in his last outing Saturday, but he had been working mainly in mop-up duty and figures to remain in that role.