Milton Bradley and Eric Chavez also homered for the Athletics, who took two of three from Baltimore to improve to 5-2 since the break. After beating up on Boston and Baltimore, the A's get a day off before beginning a weekend series against the Detroit Tigers.
"It's nice. We take three of four in Boston, and two of three here, and we've got some momentum now going into Detroit," said Zito, who allowed one run. "It will be a tough series out there, but a great series. They're a great team, so we couldn't ask for anything more than to be where we are right now."
With Zito leading the way, Oakland improved to 289-162 (.641) after the All-Star break since the 2000 season. No other team in the majors has done as well.
Before the break, Oakland dropped three of four to the Los Angeles Angels. But all seems right with the A's now, as is usually the case this time of year.
"We ran into pretty good pitching by the Angels right before the break and we were a little tired there," manager Ken Macha said. "It gave us probably more of a mental boost than anything. We were pretty energized and focused when we got to Boston, and we did a good job."
Zito (10-6) helped, pitching five solid innings against the Red Sox in a 15-3 win. He now has 53 wins after the break since 2000 -- second in the majors behind Bartolo Colon (54).
Against Baltimore, the left-hander allowed only one runner past first base through the first six innings while Oakland built a 5-0 lead. It was the 14th time in 21 starts he has gone at least seven innings, and the 12th time he yielded two runs or fewer.
"The changeup was really good today. Fastball command was good as well," Zito said.
Ramon Hernandez drove in a run for the Orioles, now 9-23 when the opposition starts a left-hander.
"Zito kept us off-balance enough so that we never could get anything going against him. When all his pitches are working, it's tough," said Kevin Millar, who scored Baltimore's lone run. "He's one of the better ones out there."
Benson (9-9) gave up five runs and nine hits in losing his fourth consecutive start. He yielded all three Oakland homers, but it was only the fourth time in 21 starts this season that the right-hander allowed as many as five earned runs.
"I don't think he was as sharp as he could be," Orioles manager Sam Perlozzo said. "I thought he had good life on his fastball, but his command wasn't quite there and his off-speed pitches weren't great, either."
Thomas put Benson in a hole in the first inning. With two outs and runners on second and third, Thomas lined a two-run single to left for a 2-0 lead.
Bradley's fourth homer -- his first since April 23 -- made it 3-0 in the fourth.
In the sixth, Bradley hit a ball down the left-field line but tripped over first base and was tagged out while he headed for second. Chavez followed with his 15th homer, and two pitches later Thomas hit No. 20 for a 5-0 lead.
In the Baltimore seventh, Millar hit a one-out double, advanced on a passed ball and scored on Hernandez's bloop to right. Corey Patterson then reached on an error, but Zito ended his strong outing by getting Chris Gomez to hit into a double play.
"It's a great feeling when you can get two outs on one pitch," Zito said, "especially battling a little bit in that last inning."
- Bradley went 3-for-4 and is 9-for-19 in five games since returning from the disabled list. All four of his homers have been solo shots.
- Chavez came in with only one extra-base hit during an 18-game span.
- Baltimore 2B Brian Roberts was given the day off, ending a run of 49 consecutive starts.
- Oakland had only 15 homers in its previous 27 games.