OAKLAND, Calif. -- Left-hander Madison Bumgarner made major league history at the plate and earned his ninth win of the season on the mound Thursday night.

Bumgarner became the first starting pitcher in 40 years to hit for himself intentionally at an American League stadium, and he led the San Francisco Giants to a 12-6 win over the Oakland Athletics at the Oakland Coliseum.

The White Sox had starting pitcher Ken Brett hit instead of using a designated hitter in two games in 1976. Pitcher Andy Sonnanstine hit for the Tampa Bay Rays in a DH game in 2009, but only because manager Joe Maddon made a mistake filling out his lineup card.

Bumgarner, who has 13 career home runs, hit a leadoff double in his first at-bat, sparking a six-run rally in the third inning when the Giants batted around. Bumgarner went 1-for-4 and had two at-bats in the third inning.

"I was happy to get a hit," he said. "A lot of people had a lot to say about what we did today. I was just glad it worked out for us."

On the mound, Bumgarner (9-4) gave up four runs on seven hits, including two home runs, over 6 1/3 innings. He struck out four, walked none and ended a personal two-game losing streak.

Buster Posey hit a three-run homer and Brandon Crawford a solo shot for the Giants -- both in the third inning. Crawford had three hits, while Posey, Brandon Belt, Denard Span, Angel Pagan and Grant Green had two apiece. Belt drove in four runs.

After losing three straight games to the A's, San Francisco salvaged a victory in the finale and stopped Oakland from becoming the first team to sweep a Bay Bridge Series.

Giants manager Bruce Bochy said it was an easy decision to have Bumgarner hit for himself.

"He's got presence in the lineup," Bochy said. "He's a pitcher, but he's imposing, he's dangerous. He's won some games for himself by handling the bat. More importantly, we won the game. You lose three in a row, you'd hate to get swept, so these guys were fighting, and they did a great job today."

A's shortstop Marcus Semien hit his 16th home run, setting a single-season high with a solo shot in the first inning. Yonder Alonso hit a two-run shot off Bumgarner in the seventh, cutting the Giants' lead to 8-4. Jake Smolinski went 3-for-4.

A's rookie left-hander Dillon Overton (1-1) gave up eight runs on eight hits, including two home runs and four doubles, in three-plus innings. Overton, who beat the Los Angeles Angels in his major league debut Saturday at Angel Stadium, lost his first career start at the Coliseum. He walked three and struck out one.

"His changeup's his pitch," A's manager Bob Melvin said. "Looked like he was just missing with some pitches that (third) inning and got some bad counts. Wasn't really able to establish that pitch. Then when he threw it over the plate, they hit him."

The A's took a 1-0 lead in the first inning when Semien homered with one out off Bumgarner, but the Giants answered with six runs in the third.

Bumgarner led off that inning with a double to right-center that went in and out of center fielder Billy Burns' glove.

"I've watched him on TV for years now, " Overton said. "I knew he could hit. First two pitches I threw to him I thought were strikes. The umpire didn't really help me out with those, which led me to just having to put one in the zone so he could call it a strike, and I left that one up and Bum made me pay for it.

"He swings the bat like he's an everyday player, swings it with passion, swings it hard, and he's trying to hit a home run every time he gets up there."

Overton walked Span, and Pagan blooped a single to left, loading the bases.

Belt drove in two runs with a ground-rule double that bounced off the warning track in left-center and over the wall. Posey followed with a three-run blast to deep left-center, and Crawford hit Overton's next pitch for a home run to right, making it 6-1 and capping a rally that Bumgarner started.

"I want to be as good a baseball player as I can be, not just a pitcher," Bumgarner said. "In this league, you got to hit. You can change the outcome of the game sometimes. You can earn a few more wins if you can handle the bat a little bit."

The Giants added two runs in the top of the fourth. Span hit a leadoff double, and Pagan followed with an RBI double that ended Overton's night. Crawford drove in Pagan with a two-out single.

Oakland cut the Giants' lead to 8-2 in the bottom of the inning when Billy Butler doubled and scored on Smolinski's single.

NOTES: The A's placed LHP Sean Doolittle (strained left shoulder) on the 15-day disabled list, retroactive to Saturday. Last year, he missed 121 games and had two stints on the DL because of left shoulder injuries. He had an MRI late Thursday afternoon that showed "subtle changes in the labrum," Melvin said. "We're just going to let it calm down for a little while. There's some inflammation in there." There is no timetable for Doolittle's return, Melvin said. ... Oakland recalled LHP Daniel Coulombe and RHP Andrew Triggs from Triple-A Nashville and optioned RHP Zach Neal to Nashville. ... The Giants recalled INF Grant Green from Triple-A Sacramento, and he started at second base against the A's. ... Giants RHP Chris Stratton was optioned to Sacramento. ... Giants INF Ramiro Pena had an MRI on Thursday that confirmed the initial diagnosis of a sprained left ankle. Pena was injured during a collision with RF Mac Williamson in the third inning Wednesday. Pena is expected to be out of the lineup for five to seven days but might be available to pinch-hit this weekend.