OAKLAND, Calif. -- After Chris Davis was called out on strikes in a full-count situation earlier in the game, the last thing the Baltimore Orioles first baseman was going to do on a 3-2 pitch with the bases loaded in the 10th inning Wednesday afternoon was go down looking.

So he swung, and then he watched.

Davis belted reliever Arnold Leon's full-count pitch over the 388-foot sign in left-center field for a grand slam, delivering the Orioles a 7-3 victory over the Oakland Athletics.

"In that situation right there, you know you can be careful," Davis said of batting with the bases loaded and one out. "I waited him out."

The win was the Orioles' second in the three-game series in Oakland and ninth in their last 12 games overall.

Catcher Caleb Joseph opened the 10th with his second hit of the game, a single against Leon (0-1), the fifth A's pitcher.

Third baseman Manny Machado sent Joseph to third with a single, after which Oakland manager Bob Melvin chose to intentionally walk right fielder Gerardo Parra to load the bases.

"With (Orioles closer Zach) Britton on the mound, we're trying to get off the best we can," Melvin said.

The strategy initially worked as Orioles center fielder Adam Jones popped out for the first out. However, Davis bombed Leon's sixth pitch of the at-bat for his 28th homer of the season.

"I was trying to be patient," Davis said, "but at the same time, know I had to protect."

Davis, who began the day third in the American League in RBIs, increased his total to 79. He now has nine home runs in his past 16 games.

"The guy knows what the team needs, and he brings it," Orioles manager Buck Showalter said. "We're getting people out there, though. You can't hit a grand slam with no one on."

Britton (2-0), the fourth Orioles pitcher, got the win with two innings of one-hit relief.

Davis, Joseph and shortstop J.J. Hardy had two hits apiece for the Orioles, who continue a nine-game Western swing with three in Anaheim against the Los Angeles Angels beginning Friday.

"Big win," Davis said of taking two of three from the A's. "This is a tough place to play. These guys always play us tough."

Shortstop Marcus Semien had a two-run double among two hits for the A's, who won three of their previous four games.

Five of Oakland's eight hits were doubles, tying a season high.

"We had some situational at-bats where we didn't get it done. Man on second and nobody out and we don't get him over to third and we don't get him in," Melvin said. "Usually in close games, those will come back and bite you."

Neither starting pitcher factored in the decision after both exited with the score tied at 3-3 in the middle innings.

A's right-hander Kendall Graveman, seeking to end a four-game winless run, took a 3-1 lead into the sixth inning before falling victim to three consecutive two-out hits.

Orioles designated hitter Jimmy Paredes and Hardy had two of the singles, each driving in a run. Hardy's hit scored Davis with the tying run. Billy Burns prevented additional scoring in the inning with a leaping catch at the center field fence to take a possible home run away from the Jones. The catch occurred after Parra had opened the inning with a bunt single.

Parra eventually scored on Paredes' hit.

Graveman gave up three runs on six hits in 5 2/3 innings. He walked one and struck out three.

Orioles left-hander Wei-Yin Chen was replaced by right-hander Brad Brach to start the bottom of the sixth. Chen struggled through five innings, allowing four hits and four walks, but limited the damage to three runs. He struck out four.

Semien had a hand in all three of Oakland's runs.

He walked and scored on second baseman Brett Lawrie's sacrifice fly in the bottom of the third inning.

The run allowed the A's to get even at 1-1 after Baltimore opened the scoring in the top of the inning on a double by second baseman Jonathan Schoop and an RBI single by left fielder Nolan Reimold.

Semien put Oakland on top 3-1 in the fourth with a two-run double that scored catcher Josh Phegley, who walked, and left fielder Mark Canha, who doubled Phegley to third.

NOTES: Orioles RHP Chris Tillman (sprained right ankle) threw a bullpen session before the game and is scheduled for another Friday in Anaheim. If all goes well, he could start the series finale against the Angels on Sunday. ... The Orioles announced that RHP Kevin Gausman will start Friday's opener against the Angels. ... A's LF Coco Crisp was a late scratch from the starting lineup because of a sore neck. He entered the game as a pinch hitter in the ninth inning, grounding out. ... 3B/OF Danny Valencia, acquired on waivers from Toronto earlier in the week, made his A's debut at third base, with Brett Lawrie moving to second. Valencia had one of Oakland's five doubles on a 1-for-5 day.