Hart was recalled from Triple-A Norfolk on Wednesday, Rich Dubroff of BaltimoreBaseball.com reports.
Hart will rejoin the Orioles' bullpen after spending the past week in the minors. Over 9.2 innings of relief with the big-league club this year, he's posted a 3.72 ERA and 1.97 WHIP with five strikeouts. Look for him to be deployed in low-leverage spots.