Cowser is starting in left field and batting seventh versus the Yankees on Wednesday in his major-league debut, Nathan Ruiz of The Baltimore Sun reports.
Cowser could wind up bouncing all over the outfield for the Orioles, but he'll play left field in his debut with Austin Hays (hip) still banged up. The rookie earned a promotion after putting together a sparkling .330/.459/.537 batting line with 10 homers and 40 RBI through 257 plate appearances with Triple-A Norfolk.