The moves were made Sunday before Oakland faced the Seattle Mariners.
Pomeranz (5-4, 3.21 ERA) had been on the disabled list since June 17 after breaking his right hand.
Pomeranz has played in 17 games for Oakland this season, the final eight as a starting pitcher. While in the rotation, Pomeranz was 4-3 with a 3.21 ERA before he was injured. He has since lost his starting spot with Oakland's acquisitions of Jeff Samardzija and Jason Hammel from the Chicago Cubs.
Oakland manager Bob Melvin said Pomeranz would remain a starter for now with the possibility of a return to the bullpen in the future.