OAKLAND, Calif. -- Adam Jones wasn't all that impressed with matching his career high for RBIs. The veteran outfielder was more concerned with the runners he and his Baltimore teammates left on base.
It's that type of thinking Orioles manager Buck Showalter hopes will lead his club deep into the postseason.
The Orioles scored more than seven runs for only the fifth time in their last 40 games but stranded nine runners -- seven in scoring position.
"Our guys, they're never satisfied," Showalter said. "It's a very professional group."
Jones hit a three-run homer in the first and had a two-run single in the fourth. Baltimore's All-Star center fielder also walked and scored in the third.
It was his two other at-bats that bothered Jones. He grounded out with runners on second and third in the sixth, then hit into a fielder's choice with two on in the eighth.
"We're a team that ... we need to fix it," Jones said. "We need to fix those type of things. That's what we need to work on."
Chen (10-3) allowed three runs over five innings with four strikeouts in an uneven outing while winning his third consecutive start. The left-hander improved to 4-0 in five career starts against the A's.
Brandon Moss hit his team-leading 22nd home run for Oakland.
One day after blowing a two-run lead in the ninth on Josh Donaldson's game-ending home run, the Orioles took a 7-1 lead, then held off another rally by the A's to move 10 games over .500.
"I just kind of stepped back during the workout on Thursday at how professional, focused and engaged they were," Showalter said. "They know the challenge ahead of them and how hard it's going to be with the schedule that we have to play the rest of the way."
Jones provided the bulk of the offense with the second five-RBI game of his career. He also drove in five against the New York Yankees on July 28, 2008.
Markakis helped with his third four-hit game of the year. All four hits were singles. He also reached on an error in the eighth.
The Orioles needed it on a night when Chen was inconsistent. He retired the first six hitters before giving up Moss' home run leading off the third. Chen also gave up a two-run double to Jed Lowrie in the fourth.
Lowrie added an RBI single in the sixth off reliever Brad Brach.
Zach Britton retired one batter for his 16th save of the year.
The A's had won seven straight at home before losing in front of a sellout crowd on hand to celebrate the 25th anniversary of the franchise's 1989 World Series championship.
Oakland starter Jason Hammel (0-2) gave up five runs in two-plus innings, his second rocky outing since being acquired from the Chicago Cubs along with All-Star pitcher Jeff Samardzija in a trade on July 5.
"His command of the heater wasn't very good and he got into some bad counts and they made him pay," A's manager Bob Melvin said. "We had a lot of trouble with the top of their lineup."
Baltimore knocked Hammel out of the game with four runs in the first and another in the third.
Markakis singled to lead off the game, Steve Pearce walked and Jones followed with his 17th home run to break an 0-for-10 skid. Hardy added a solo shot with two outs to make it 4-0.
Jones walked in the third and scored on Davis' RBI double.
Davis hit his 16th home run in the ninth off former A's closer Jim Johnson.
Former A's pitcher Dave Stewart threw out the ceremonial first pitch as part of the 25th anniversary celebration. Members of that team, including Jose Canseco and Rickey Henderson, laid flowers at the base of the pitching mound where Bob Welch's No. 35 was inscribed during a pregame ceremony. Welch, who played on the `89 team, died of a heart attack in June. ... Sonny Gray (10-3) pitches the series finale for Oakland and is unbeaten in his three July starts this season. RHP Kevin Gausman (4-2) pitches for Baltimore.