The Astros, trying to battle their way back into the National League Central chase, moved within one game of .500.
Bud Norris, called up from Class AAA Round Rock after the All-Star break, won his second major league start.
Norris (2-0), who was a sixth-round draft choice of the Astros three years ago, limited the Brewers to two runs on three hits over six innings. He struck out seven.
Jason Kendall gave Milwaukee a 2-1 lead with a two-run homer in the fifth, but Michaels and Miguel Tejada hit solo shots in the bottom half of the inning to put Houston back in front.
Michaels came through with his three-run homer in the next inning to break open the game.
Four Houston relievers combined to allow a run on five hits over the final three innings, with Jose Valverde earning his 14th save.
Carlos Villanueva (3-8) gave up four runs on six hits in 5 1/3 to take the loss.
Copyright 2009 by United Press International.