With the victory, Baltimore took the three-game series and trails Oakland by just two games for the second American League Wild Card spot. The A's, who lead the Indians by 1 1/2 games in the Wild Card race, have lost five of eight and are 16-18 since the All-Star break. Oakland remains 2 1/2 games behind Texas in the AL West standings.
"A lot of the hits early were not hard, but they did made him work a little bit later and they made him throw some pitches," manager Bob Melvin said about Gray. "Maybe his stuff wasn't as good, but it was a little bit of a product early on of getting dinked a little bit. I don't think anyone goes through their career without getting hit some. He'll probably be better for it next time around."
Gray (1-2) allowed a season-high eight hits with three strikeouts and two walks. He threw 67 pitches and saw his ERA rise from 1.44 to 3.18.
Josh Donaldson hit his 19th home run for the A's. Reddick reinjured his right wrist while batting in the sixth and left the game.
There was no definitive prognosis immediately following the game. Reddick said it was "50-50" on whether he would have to go on the disabled list.
"I'm not going to be stupid about it again," Reddick said. "We'll see where we are tomorrow, reevaluate and go from there."
Orioles starter Scott Feldman overcame some shaky moments in his five-inning start, allowing just one run on three hits with six strikeouts and four walks on 102 pitches. He also committed a balk and hit a batter.
Chris Davis went 2-for-4 and got his 118th RBI for the Orioles, while J.J. Hardy hit his 23rd home run. Nick Markakis also picked up his ninth homer and Manny Machado went 2-for-2 with two RBIs. Nate McLouth added further damage by going deep for the ninth time this season.
Oakland took a 1-0 lead in the first on a bloop single by Alberto Callaspo that scored Coco Crisp, who walked to open the game and then took second on the Feldman balk.
The Orioles responded by scoring twice in the bottom half of the inning on an RBI single by Adam Jones and a sacrifice fly by Matt Wieters. Baltimore then increased the lead to 5-1 in the second on a single by Brian Roberts, a sacrifice fly by Machado and another single by Davis.
Machado hit another sacrifice fly in the fourth to provide a five-run margin, ending Gray's afternoon. It was the first time since 2000 the Orioles had three sacrifice flies in one game.
"I felt good," Gray said. "My stuff has been better. I just didn't make a lot of pitches that I needed to. They weren't really hitting the ball that hard, but they were finding holes. It wasn't our day and it started with me in the first inning."
Lefty Jerry Blevins allowed a home run to Hardy to open the sixth and Oakland trailed, 7-1. The Orioles lead the Majors with 175 homers and have gone deep in 103 of their 129 games.
Donaldson's two-run shot off lefty T.J, McFarland in the eighth pulled the A's to within 7-3. However, Markakis and McLouth answered for Baltimore in the same inning with homers to right.
"I'll admit -- coming in today, there's not many days when I go, 'We need to play well today and see if we can get a W,'" Orioles manager Buck Showalter said. "This was one of those days. Plus we got such great support the last three days, well the whole season. But the energy in the ballpark, our fans have been so supportive."
The A's hope to get a boost with their rotation Monday in Detroit when Bartolo Colon (groin) and Brett Anderson (foot) will throw bullpen sessions to see if they are healthy enough to rejoin the team.