OAKLAND, Calif. -- The Baltimore Orioles scored a combined three runs in the first three games of their series against the Oakland A's, losing all three by one run.

Mark Trumbo drove in four runs with one swing of the bat Thursday, and the Orioles rode his third career grand slam to a 9-6 victory against the A's in the series finale at the Oakland Coliseum.

Trumbo belted his major-league-leading 32nd home run of the season and first grand slam as an Oriole in the fifth inning, extending Baltimore's lead to 7-0. He hit reliever Daniel Coulombe's 3-1 pitch high and deep over the left-center-field fence. Trumbo went 2-for-4, scored twice and drove in a season-high-tying five runs.

Trumbo came into the game on an 0-for-13 skid.

"There's been a sprinkling of hard contact, but overall the at-bats haven't been that great," Trumbo said. "That's something I try not to look too far into. The effort's still there. I made a little bit of an adjustment today and I think it worked out all right."

Adam Jones hit his 23rd home run of the season, a solo shot in the seventh inning off right-hander Chris Smith for the Orioles. Pedro Alvarez went 2-for-4 with a two-run double and three RBIs, Chris Davis went 2-for-4 with a walk and scored twice and Manny Machado had two hits, including a double, and scored twice.

"They were a little ornery today," Orioles coach Buck Showalter said. "You could tell there was a quiet confidence. That's why they're so easy to trust. This is who we are and how we have to do it. I've got a lot of trust in them and hopefully them in us as a coaching staff.

"They're not going to panic. We're trying to grind like heck to have a chance to roll the dice in August and September."

Right-hander Chris Tillman (15-4) allowed two runs on five hits in seven innings and struck out five without walking a batter. He is tied for second in the major-leagues in victories with Boston's Rick Porcello and Washington's Stephen Strasburg, one behind Toronto's J.A. Happ. Tillman snapped a personal two-game losing streak.

"The fastball command was spotty, wasn't very consistent, but the other pitches were there for me throughout," Tillman said. "I felt we were able to make pitches when we had to, to get some key outs."

Rookie Ryon Healy launched his fourth home run of the season for the A's, a two-run blast in the fifth inning. Max Muncy hit a solo shot in the eighth, his second home run of the season. Yonder Alonso had a two-run double in the eighth.

"You find out the character of a younger player when he comes up, starts out really good and goes through some harder times," A's manager Bob Melvin said of Healy.

"They're making some better pitches on him. We've seen and we know that he's a fighter, so to come back and make some good plays and hit the ball well and hit the ball out of the ballpark again, your game kind of surfaces again because of the fight that he has and certainly because of the ability that he has."

A's right-hander Andrew Triggs (0-1) made his second start of the season and gave up three runs on five hits over four innings. He struck out four and walked none. Triggs, who made 19 of his first 20 outings in relief, filled a void in an A's rotation that has been hit by numerous injuries.

The Orioles took a 3-0 lead in the fourth inning.

Machado, Davis and Trumbo hit consecutive one-out singles off Triggs, making it 1-0. Then Alvarez hit a two-run double to the right-center-field alley, scoring Davis and Trumbo.

"It's hard to shut a team like that down four games in a row," A's catcher Stephen Vogt said. "It's not like you sit back and expect it, but there's definitely an uneasy feeling whenever any of those guys step in the box because one through nine they can hit the ball out of the park at any moment."

In the fifth, Jones hit a one-out single and took second on left fielder Coco Crisp's fielding error. Machado was walked intentionally with two outs, and Davis worked a walk off Coulombe, loading the bases. That set the stage for Trumbo's first blast since Aug. 4.

"He's had a good season," Showalter said of Trumbo. "Just because he hasn't been perfect the last week or so, there's a lot of people that would trade places with him right now statistically. We're lucky to have him or we wouldn't be where we are."

The A's cut Baltimore's lead to 7-2 in bottom of the fifth. Billy Butler lined a leadoff single, and Healy launched Tillman's 3-1 pitch for a home run to left field with one out.

Jones answered with a solo home run leading off the seventh, and Alvarez added an RBI single to make it 9-2.

The A's scored four times in the eighth, cutting Baltimore's lead to 9-6. Muncy lined a leadoff homer to right. Alonso hit a two-run double, and Butler followed with an RBI single.

Baltimore's Zach Britton pitched a scoreless ninth, despite allowing a walk and two singles, for his 35th consecutive save to start the season. He leads the American League in saves.

NOTES: Orioles SS J.J. Hardy was out of the starting lineup and utility man Ryan Flaherty started at shortstop for the third time this season. ... Orioles OF Steve Pearce (strained right elbow) missed his fourth straight game. The Orioles have yet to decide whether to put him on the 15-day disabled list. ... Athletics RHP Jesse Hahn (strained right shoulder) will throw his first bullpen session on Saturday since going on the 15-day disabled list Aug. 5. According to manager Bob Melvin, Hahn will likely make a rehab start next week and be activated on Aug. 20, the first day he is eligible to come off the DL, or soon after. ... Orioles 2B Jonathan Schoop made his 114th consecutive start this season. He is the only Oriole to start every game.