BALTIMORE -- Zach Britton doesn't feel like a rookie when he's on the mound, and he certainly doesn't pitch like one.

Even though he's only five starts into his big league career, the left-hander is already looking like an ace.

Britton allowed one run in six innings to earn his fourth win, Derrek Lee had two hits and scored twice, and the Baltimore Orioles beat the Red Sox 4-1 Tuesday night to end Boston's five-game winning streak.

Britton (4-1) became the first rookie starter in franchise history to win four games in April. He has an impressive 2.84 ERA and owns nearly half of Baltimore's nine victories this year.

"So far he's been good. He's handled it pretty well for a guy with limited experience," Orioles manager Buck Showalter said. "We like the things he's doing right now."

Britton gave up five hits, walked two and struck out two. It was the third time he permitted one run or fewer.

Not only that, but the 23-year-old has the poise of a veteran.

"I really don't get that nervous out there," Britton said. "I don't know what it is. It's not that I have a huge ego or anything. I have a lot of confidence that I can get out of the jams, and if I'm out there getting all worried I think the situations blow up. So I try to take my time and take a couple breaths and get after it."

No rookie starter with the St. Louis Browns or Baltimore Orioles ever won more games in April, but Britton didn't seem to care about his piece of history.

"I think I've gone out there and given this team an opportunity to win every time out, and that's my goal," he said. "It's not about setting a record for wins in a month for a rookie or anything like that. It's not about having a sub-3 ERA. It's about keeping our team in the game every time out, and that's what I am hoping to continue to do."

Britton sure impressed the Red Sox. Left-handed hitter David Ortiz, who went 1 for 2 with a walk against the rookie, said, "He's super-tough on righties. He's a young kid who just come in the league. It seems like he has good stuff. He was hitting 95 [mph]."

Adam Jones drove in two runs for the Orioles, who won for only the third time in 14 games, and Vladimir Guerrero had his first three-hit game since coming to Baltimore as a free agent during the offseason.

After Britton left, Jim Johnson notched four strikeouts in two innings and Kevin Gregg worked a perfect ninth for his third save.

Boston starter Clay Buchholz (1-3) yielded four runs and 12 hits in 6 2/3 innings, his longest outing of the year.

"I thought I threw the ball better tonight than I did in the earlier game [against Oakland] when I got a win out of it," Buchholz said. "I felt like I was throwing all my pitches for strikes. They sat back and hit a couple of good curve balls."

Kevin Youkilis drove in the lone run for the Red Sox, who managed only six hits. Boston had won eight of nine and was vying to reach .500 for the first time this season.

"[Giving up] four runs with the way [Britton] was pitching was too much," Red Sox manager Terry Francona said.

Baltimore ended Boston's run of 19 straight scoreless innings while taking a 1-0 lead in the second. Luke Scott singled, took third on a one-out double by Mark Reynolds and scored when Matt Wieters' bouncer hit first base for a single. Buchholz then struck out Robert Andino and Brian Roberts.

The Orioles used two singles, a walk and a sacrifice fly by Jones to go up 2-0 in the third.

Boston closed to 2-1 in the fourth when Dustin Pedroia singled, advanced on a groundout, stole third and scored on a fly ball by Youkilis.

The Red Sox loaded the bases with two outs in the fifth before Adrian Gonzalez grounded into a fielder's choice.

In the bottom half, Lee and Guerrero singled before Jones hit a run-scoring fly to center. Reynolds chased Buchholz with a sacrifice fly in the seventh.

Game notes

Wieters was 7 for 7 with 11 RBIs with runners in scoring position before grounding out with two on in the seventh. ... Boston starters have a 1.33 ERA over the last 10 games. ... Roberts extended his hitting streak to 12 games with a sixth-inning single. ... Buchholz was 5-2 lifetime against Baltimore and 3-0 in his previous three starts at Camden Yards.