The NL Central leaders improved the best record in the majors to 21-9 and opened a 7½-game lead over Cincinnati. The Brewers are 12-3 on the road.
Peralta (4-1) made his fifth quality start of the season, holding the Reds to three hits and a pair of walks while throwing 110 pitches. Francisco Rodriguez retired the three batters he faced for his 14th save in as many chances.
Peralta doubled with two outs in the fifth off Mike Leake (2-3), who left his first pitch over the plate. Leake gave up seven hits and fanned five as he went eight innings for the second time this season.
Right fielder Ryan Braun missed his sixth game with a sore muscle on his right side. The Brewers will decide this weekend whether he's close to returning or needs time on the disabled list.
Peralta put the Brewers ahead with his 10th career hit.
Lyle Overbay opened the fifth with a single and Caleb Gindl walked with one out. Jean Segura forced Gindl at second, bringing up Peralta, who had struck out in his first at-bat. He doubled to right field on the first pitch. Peralta is 10 for 72 in his career with 30 strikeouts.
Peralta made it stand up by escaping scoring threats in the first, fourth, fifth and sixth innings. He fanned Jay Bruce three times with runners in scoring position. Bruce also struck out in the ninth.
Reds leadoff hitter Billy Hamilton was out of the lineup with a sore left hand, which he sprained while making a diving catch during Cincinnati's 8-3 win in the series opener Thursday night. He was available to pinch-run.
Joey Votto, robbed at the top of the wall by center fielder Carlos Gomez on Thursday night, hit a flyball that deflected off the top of the wall in left field and bounced back into play in the fourth inning. Votto wound up with a double, and the call was upheld upon review. Votto was stranded at second.
The Reds put runners on second and third with two outs in the fifth when Ramon Santiago drew a walk and Segura threw wildly to first on Leake's grounder to shortstop. Peralta retired Chris Heisey on a grounder to end the inning.
NOTES: Yovani Gallardo (2-0) faces Johnny Cueto (2-2) in the third game of the series. Cueto has allowed only one run in his last 30 innings. ... The Reds made it a Star Wars theme night. ... It was Milwaukee's third shutout. The Reds were blanked for the fourth time. ... Brewers 3B Aramis Ramirez extended his slump to 0 for 29. ... The Brewers put reliever Jim Henderson on the 15-day DL with a sore shoulder. Gindl was called up from Triple-A Nashville. ... Reds closer Aroldis Chapman will pitch another inning for Class-A Dayton at Lake County on Saturday, then join Triple-A Louisville to continue his rehab assignment. He's recovering from a line drive off his forehead on March 19 and could be activated next week.