Molina's blast in the sixth inning put the Cards ahead 5-3 and Skip Schumaker added some a insurance with a two-run double in the eighth for St. Louis, which clinched its three-game series with the Brewers.
Jon Jay added three hits and an RBI for St. Louis, which pounded Milwaukee 13-1 in Friday's series opener.
Kyle Lohse (4-0) won for the fourth time in five starts to begin the season, holding the Brewers to three runs on six hits over six frames, walking four and striking out five.
Milwaukee's Marco Estrada (0-1) absorbed the loss, surrendering five runs (four earned) on seven hits in a six-inning start.
Easer Egg Roll brings thousands to White House
Yosemite climber falls 30 feet, suffers major injuries