SAN FRANCISCO -- When Jake Peavy looked up at the American flag above the AT&T Park bleachers on Independence Day, he didn't focus on the stars or stripes Monday.

Rather, he noted a stiff wind and knew it was going to be a good day for the San Francisco Giants.

Peavy recorded 12 of 20 outs on fly balls while limiting the Colorado Rockies to one run over 6 2/3 innings in a 3-1 Giants win. The result was the right-hander's first victory on July 4 in his 15-year career.

"I'd like to think I'm as patriotic as anybody," the Alabama native said. "The adrenaline rush you get when you see the flag, the troops. That's meaningful to me."

On a sunny and windy afternoon by the San Francisco Bay, equally meaningful were the 12 catches by an outfield consisting of minor league call-ups Mac Williamson and Jarrett Parker on the flanks and Angel Pagan in center.

"You are concerned when the ball goes in the air here. I'm not going to lie to you," Peavy said. "The wind, the sun ... they can play tricks on you. That gives us a huge home-field advantage."

Buster Posey and Pagan rode the wind for home runs off Rockies left-hander Tyler Anderson, helping the Giants open a six-game homestand on a positive note.

The loss was the Rockies' sixth in a row.

"Anderson did a real nice job," Rockies manager Walt Weiss said. "He's done a nice job each time out for us. Unfortunately, we haven't been able to get him a win, but he put us in a position to win."

Peavy balked in a run in the second inning before keeping the Rockies scoreless until turning the ball over to the San Francisco bullpen with two outs in the seventh.

Five relievers combined to record the final seven outs, with closer Santiago Casilla getting the final three for his 20th save.

Peavy (5-7) lost to the Giants in 2003 while pitching for the San Diego Padres in his only previous start on Independence Day. On Monday, he allowed five hits and two walks and struck out six while winning for the third time in his past four decisions.

Like Peavy, Giants manager Bruce Bochy credited the outfield with an assist on the 35-year-old's 152nd career win.

"In a close game like that, the defense usually plays a part," Bochy said. "This is a tough outfield in day games. Then we have two young kids on the corners and Angel, who hasn't played center all year. They did a good job."

The only run Peavy allowed came after the Rockies loaded the bases in the second inning on a Ryan Raburn double, a Mark Reynolds single and a Nick Hundley walk.

With Anderson at the plate, Peavy pivoted and made a pickoff throw to first baseman Brandon Belt, who was not covering the base. Belt was able to catch the throw, but it was ruled a balk because it was not deemed a legal pickoff attempt.

"I'm confused," Peavy said of the ruling.

He nonetheless went on to strike out Anderson and retire Charlie Blackmon on a popout to escape further damage.

Posey's home run leading off the bottom of the second got the Giants even. It was his 10th of the season.

Pagan provided the difference-making blow in the third after Ruben Tejada opened the inning with a single.

The switch hitter, batting right-handed, took Anderson into the left field bleachers for his fourth homer of the season.

"It looked like he was a little off balance," Anderson said of Pagan. "But he's a strong man, and even though he was out in front, he was able to keep the barrel on it. That ball was elevated."

Anderson (0-3) had allowed only one home run to the first 100 batters he faced in his major league career before Monday.

The former first-round draft pick was pulled for a pinch hitter after six innings. He gave up the three runs on just four hits and a walk while striking out two.

Jake McGee, Gonzalez Germen and Boone Logan kept the Rockies within striking distance with two innings of shutout relief.

Pagan added a double to his home run to lead a five-hit attack for the Giants, who took a 6-5 lead in the season series over the Rockies.

Pagan's double came on a fly ball that was lost in the sun by Blackmon, the Rockies' center fielder.

The Rockies had two other near-collisions on wind-blown fly balls.

Weiss credited Anderson for keeping things as easy as possible on his defense.

"He's really good from the neck up; he's got a good feel for pitching," the manager said. "He's going to be a good one."

Nolan Arenado had a pair of doubles for the Rockies, who totaled just two runs in losing three straight to the Los Angeles Dodgers in their series that ended Sunday.

The doubles were Arenado's seventh and eighth in the 11 games against the Giants this season.

NOTES: The Giants have won 22 of their last 27 games against National League West competition. ... San Francisco is 4-0 at home against the Rockies on July 4. ... The Giants improved to 21-9 in day games, tying the Los Angeles Dodgers (14-6) for the best record in the majors. ... Rockies SS Trevor Story (bruised right middle finger) made his first start since June 28. He went 0-for-3 with a walk and a strikeout. ... Rockies manager Walt Weiss confirmed before the game that RHP Tyler Chatwood (mid-back strain) would be reinstated from the disabled list in time to start Tuesday's second game of the series. ... The Giants made a series of roster moves before the game, reinstating RHP Sergio Romo (straight right flexor) from the DL, demoting RHP Albert Suarez to Triple-A Sacramento and designating RHP Mike Broadway for assignment. Romo faced two batters in the eighth inning, allowing one of 3B Nolan Arenado's two doubles. ... Monday was the 33rd anniversary of Giants pitching coach Dave Righetti's no-hitter for the New York Yankees over the Boston Red Sox.