The Orioles purchased the contracts of catcher Michael Ohlman and left-handed pitcher Tim Berry from Frederick, and right-handed pitcher Eddie Gamboa from Norfolk.
With the signing of Edgmer Escalona earlier in the day, the Orioles have 36 players on the 40-man roster.
Ohlman batted .313 with 13 home runs, 53 RBIs and was named the Carolina League Player of the Year.
Berry was a 50th round draft pick in 2009 and was 11-7 with a 3.85 ERA for the Keys.
Gamboa, who was converted to a knuckleballer this season, was 6-11 with a 4.43 ERA with Bowie and Norfolk.
Caleb Joseph, who hit 22 home runs with 97 RBIs at Bowie, was not added to the 40-man.