BALTIMORE -- With plenty of backing from his new teammates, Jason Johnson earned another victory against his former club.
Johnson (2-0) allowed one run and seven hits in seven-plus innings. He struck out two and walked none.
"It is fun to be on a team like this one," said the right-hander, who spent the last two seasons in Detroit. "Every time I take the mound, I expect to win."
Signed as a free agent in December, Johnson lowered his ERA to 1.83 in three starts with Cleveland. He's 4-1 with a 3.04 ERA lifetime against Baltimore, where he played from 1999-03.
"It's always fun to pitch here," he said.
Especially when your team scores 15 runs.
"I treated it as if it were a 1-0 game," Johnson said. "I'm still going for a complete-game shutout. I'm not thinking about anything else. I was upset when I gave up the run in the eighth. I wanted to finish it."
Johnson was lifted after giving up an RBI double to Brian Roberts. Danny Graves and Scott Sauerbeck finished the seven-hitter.
Sizemore had three hits, Martinez went 3-for-6 to extend his hitting streak to 13 games and Casey Blake went 3-for-4 to raise his batting average to .447. Ben Broussard entered as a pinch hitter in the fifth inning and went 3-for-4 with two RBI.
The 15 runs were the most scored by the Indians this season, and the outburst came on the heels of a 10-run effort one night earlier in Detroit. Cleveland hadn't reached the 20-hit mark since last June against Cincinnati.
Roberts tied a career high with four hits, going 4-for-4 with an RBI and two stolen bases. But that was the lone highlight for the Orioles.
"You have to forget about it and look forward to tomorrow," Baltimore manager Sam Perlozzo said. "There's nothing else to do. We've been playing good baseball and we had a game where everything kind of fell apart on us."
Bruce Chen (0-2) gave up eight runs and eight hits in four innings, including both Cleveland homers. He has yielded six home runs in his last two starts.
Jason Michaels gave Cleveland a 2-0 lead in the third inning with a two-out, two-run single.
Cleveland pulled away with a five-run fourth. After Travis Hafner drew a leadoff walk, Martinez hit his second homer of the season. Chen then gave up a single and a walk before Sizemore homered on an 0-1 pitch.
"We got to (Chen) early and kept going. We got into the groove," Sizemore said. "We all kind of got off to a slow start last season, so we have really made a point of focusing on scoring this season."
Jhonny Peralta and Hafner opened the fifth with singles to chase Chen, and Chris Britton gave up an RBI single to Broussard.
Cleveland didn't need any help, but the Orioles provided it in the sixth inning, making two errors and a mental gaffe during a five-run outburst that made it 13-0. Baltimore shortstop Miguel Tejada couldn't handle a cutoff throw, allowing a run to score, and Roberts let a potential double-play grounder to second go through his legs. Broussard then hit a lazy fly ball to right-center that Nick Markakis and Jay Gibbons let fall between them.
"It's not a good thing, and I'm not saying it's understandable either," Perlozzo said. "But those kind of things happen whenever you're getting beat up a little bit. It's still not an excuse; it shouldn't happen."
Blake hit a two-run single in the eighth.
Roberts' stolen bases were his first of the season. He had 27 last year. ... The Indians have had least 10 hits in 10 of their 14 games. ... Boone left in the eighth with a bruised left wrist after being hit by a pitch from Jim Brower. X-rays were negative. ... Baltimore recalled RHP Eddy Rodriguez from Triple-A Ottawa after the game and put LHP Tim Byrdak (elbow) on the 15-day DL.