Fowler, whose stint on the DL is retroactive to June 27, is hitting .270 with six homers and 24 RBIs.
Houston added left-hander Kevin Chapman, infielder Kike Hernandez and outfielder Domingo Santana.
Chapman has a 0.94 ERA in 26 games in Oklahoma City. Hernandez hit .336 with nine home runs and 36 RBIs in 77 games between Double-A Corpus Christi and Oklahoma City.
Santana hit .304 with 13 homers and 52 RBIs for Oklahoma City this season. He ranks second in the Pacific Coast League in hits.