The Phillies' lead over San Francisco in the wild-card race remained 1½ games, while the Dodgers fell 6½ back with their third loss in four games.
Kyle Kendrick (9-7) allowed four runs and seven hits in five-plus innings, walked one and failed to record a strikeout for the first time this season.
After being held to two runs or less in eight of their previous 12 games, including a shutout loss Monday night in which they managed just one hit, the Phillies got going early against Carlos Monasterios (3-5) and then kept up the pressure on the Dodgers' shaky bullpen.
Monasterios gave up a leadoff double to Jayson Werth in the second. After Raul Ibanez flied out, Shane Victorino walked and Schneider homered to right on the first pitch he saw, putting the Phillies in front 3-1.
Monasterios allowed five runs and five hits in two-plus innings, struck out one and walked one in his shortest outing of the season. The right-hander fell to 0-5 in his last seven starts.
He was yanked with runners at the corners after allowing singles to Placido Polanco and Chase Utley to open the third. Ramon Troncoso came on to face Howard, who sent a 1-0 pitch into the left-field pavilion for his 24th homer, extending Philadelphia's lead to 6-1.
George Sherrill, the Dodgers' third reliever, walked three batters - one intentionally - to load the bases. He turned it over to former closer Jonathan Broxton, who gave up a two-run single to pinch-hitter Carlos Ruiz, making it 8-4.
The Dodgers led 1-0 after Kendrick yielded a bases-loaded walk to James Loney in the first. But Kendrick got Casey Blake to ground into an inning-ending double play to minimize the damage.
Los Angeles added a run in the fifth on Jamey Carroll's RBI groundout, and Loney hit a two-run homer in the sixth, making it 6-4.
Left fielder Scott Podsednik made the defensive play of the game, grabbing Utley's fly ball in the seventh before tumbling face-first into the stands as a fan reached for the ball while holding a cell phone in his other hand.
NOTES: Dodgers RHP Kenley Jansen, who began his pro career as a catcher, singled up the middle for his first major league hit in the fifth. ... Dodgers INF Ryan Theriot didn't start after feeling pain behind his left knee from tagging out Werth a night earlier, but he pinch-hit in the sixth. ... The Phillies improved to 34-33 on the road this season.