Peralta (7-9) allowed seven hits and two walks while striking out eight, continuing a recent torrid streak. The right-hander has yielded only one run over 21 1/3 innings.
Logan Schafer went 2-for-3 with a solo homer and Carlos Gomez keyed a three-run first inning with a two-run single as the Brewers salvaged one win in a four-game road series.
Arizona's Ian Kennedy (3-6) was hung with the loss, surrendering five runs on nine hits over 6 1/3 innings.
Miguel Montero clouted a bases-empty homer for the National League West-leading D-backs.