The Orioles made the moves before Saturday's game against the New York Yankees.
Betemit had been out since Aug. 12 with an injured right wrist. He is hitting .264 with 12 home runs and 37 RBIs this season. He played two rehabilitation games at Double-A Bowie and hit a grand slam.
Avery has hit .233 in three stints with Baltimore this year. Exposito and Tolleson also have played for the Orioles this season.