Los Angeles missed out on a chance to gain ground in the National League West pennant race, remaining 4 1/2 games behind San Francisco.
The Padres took a 3-0 lead in the first with one of the runs being unearned thanks to a throwing error by Los Angeles shortstop Hanley Ramirez.
Ramirez then scored the first Dodgers' run in the second on a single by Luis Cruz and an RBI single in the fifth by Ramirez brought about a tie game.
The Padres produced the winning run off Shawn Tolleson (1-1), the second Los Angeles pitcher who worked both the sixth and seventh innings.
Will Venable drew a leadoff walk from Tolleson in the seventh, stole second and went to third on a single by Chase Headley.
That brought up Quentin, who lifted a fly ball to center on an 0-1 pitch that brought home Venable.
Nick Vincent (2-0), who worked 1 1/3 innings of hitless relief, picked up the win. Five more relievers worked the final three innings without giving up a hit or a walk.
When Luke Gregerson hit a batter with two out in the ninth, however, Tom Layne came on to face Adrian Gonzalez. Layne retired Gonzalez on a grounder to second at the end of an eight pitch at-bat to record his second save.