Marquis (6-2) has won five consecutive starts for the first time since 2007 with the Chicago Cubs. He allowed two runs, one earned, on three hits in six innings while striking out three and walking four.
"Obviously, I got away with more mistakes probably a few years back, but I feel like I'm making better pitches in bigger situations now," Marquis said. "I've learned to slow the game down more than anything. Years past, when you're younger and you maybe have a little extra on your fastball, you tend to speed things up -- harder, harder, harder. I try to stay away from the big inning and learn to focus on that pitch at that particular moment instead of the big picture."
San Diego's only major offseason move was to re-sign Marquis for $3 million, and it's paid off.
"He's a guy that continues to make pitches when he needs to," manager Bud Black said. "He knows how to navigate his way through a major league game. He gets on some nice rolls where he retires some hitters and makes it look easy."
Marquis got out of jams in the second and third.
The Cardinals tied it at 1 in the second when Chase Headley, San Diego's Gold Glove third baseman, booted Miller's bases-loaded grounder for an error with two outs, allowing Yadier Molina to score. Marquis got to a full count against Matt Carpenter before striking him out.
In the third, the Cardinals had runners on first and third with no outs after Carlos Beltran doubled and Matt Holliday singled. Beltran scored on Allen Craig's double-play grounder before Marquis got Molina to ground out to end the inning.
Chris Denorfia went 3 for 3 with an RBI for the Padres, who have won three straight and five of seven. Huston Street pitched the ninth for his 11th save in 12 chances.
Venable hit his seventh homer of the season, a drive into the Jack Daniel's Old No. 7 Deck atop the right-field fence leading off the seventh. It came on the second pitch from Mitchell Boggs, who just returned from a demotion to Triple-A Memphis.
The Padres chased Miller in the sixth, when they scored two runs on three walks, one hit and a hit batter. The rookie threw 107 pitches.
"It seems like 20 pitches every single inning, every single outing, back-to-back starts," Miller said. "Throwing so many pitches in back-to-back games is not good. It accumulates with a little bit of everything. My curveball wasn't really good tonight. Neither was my changeup. My fastball wasn't really there. Multiple things were off."
With the Cardinals leading 2-1, manager Mike Matheny pulled Miller after his second walk of the inning, with two outs. Denorfia greeted Fernando Salas with an RBI single. John Baker walked to load the bases and Salas hit pinch-hitter Jesus Guzman with a pitch to bring in another run.
Miller (5-3) allowed three runs and five hits in 5 2/3 innings, struck out five and walked three.
He entered with a 1.40 ERA, tied with Clayton Kershaw of the Los Angeles Dodgers for the lowest in the majors. It went up to 1.74. Two starts earlier, Miller allowed a single to start the game and then retired the next 27 batters in a 3-0 home win against Colorado.
Miller's scoreless streak of 14 2/3 innings ended in the first when Everth Cabrera hit a leadoff single and scored on Headley's one-out single.
San Diego had a prime opportunity to score in the third when Cabrera hit a leadoff triple to right-center. But he was stranded when Miller struck out Venable and Headley before Carlos Quentin popped up.
Headley snapped a streak of 67 consecutive games without an error dating back to Aug. 21, when he misplayed a grounder in the second inning. He had 156 chances in between errors. ... Cardinals 3B David Freese was a late scratch due to getting three stitches in the base of his right thumb after getting spiked by Milwaukee's Norichika Aoki while tagging him out during a rundown Sunday. Freese was replaced by Ty Wigginton, who grew up in suburban Chula Vista. ... Marquis has a 2.27 ERA during his five-game winning streak. ... The series continues Tuesday night when St. Louis RHP Adam Wainwright (5-3, 2.51 ERA) faces RHP Edinson Volquez (3-4, 5.55).