Dominguez went 2-for-3 with five RBI for the Astros and Carlos Pena hot a home run and drove in three runs.
The flurry of runs was more than enough for Jordan Lyles (4-1), who pitched seven strong innings and won his third consecutive decision. Lyles, who hasn't lost since May 12, held Milwaukee to one run on seven hits and struck out five.
Houston won for the fifth time in six games. Milwaukee, which had three errors in the game, has lost four of its last six.
Scooter Gennett drove in the lone Milwaukee run. Alfredo Figaro (1-1) took the loss after allowing five runs -- four earned -- on five hits over 4 1/3 innings.