BALTIMORE -- One thing Jason Bay learned rather fast upon arriving with the Red Sox is that the team has more home venues than just Fenway Park. But even he had to be somewhat taken aback by just how loud the roars were when his second home run -- a two-run shot over the wall in center in the top of the eighth -- blasted off his bat in Monday's 6-3 victory over the Orioles.

If the Red Sox have a true home away from home, it has to be Camden Yards, a venue the New Englanders always flock to in big numbers.

"To be honest with you, it didn't even occur to me that we were on the road, even in warmups," said Bay, who went 3-for-5 with four RBIs. "And they had told me that when we came here, it was going to be like that a lot. That's something I'm definitely not accustomed to. Pretty neat. It was a pretty neat little experience."

Behind Bay's first multihomer game in a Boston uniform and Jason Varitek's first long ball since July 21, a two-game losing streak was upended by the Red Sox.

All in all, it was just the type of start the defending World Series champions were looking for on a night they opened a nine-game road trip.

"We've got to win," said Red Sox slugger David Ortiz. "This is the last six weeks of the season. Tampa Bay has been an unbelievable ballclub. We've got to dig in now."

With the Rays winning again, the Red Sox (72-53) remained 4 1/2 games back in the American League East while maintaining a 1 1/2-game lead on Minnesota in the Wild Card standings.

Ultimately, the Red Sox will go as far as their pitching takes them.

In this one, Jon Lester continued his breakout season by stifling the Orioles (60-64) over his seven innings of work. The lefty allowed four hits and one run while striking out five, running his record to 12-4 and lowering his ERA to 3.17. It was Lester's 16th quality start, tying Tim Wakefield for the team lead.

Perhaps the most telling stat regarding Lester this season is that he's 6-1 in 11 starts following a Boston loss.

"You want to go out every five days and give quality starts," said Lester. "Whether we lost the game before or won the game before, it doesn't really matter. You want to go out and pitch your game, and hopefully, we end up wining."

The lefty's coming of age has been one of the better stories of the season.

"He's standing out there like he's 6-foot-4, left-handed, strong kid," said Red Sox manager Terry Francona. "I'm sure if you ask him, the game has slowed down for him. He's accumulated some innings, he's gotten some experience, he executes pitches. He gets it and throws it -- works quicker than he used to. He's got that cutter. He's got some two-seam movement with some velocity behind it. He's got a lot of ways to get you out."

Losing pitcher Jeremy Guthrie (10-9) nearly matched Lester, giving up five hits and two runs over his seven innings.

The Red Sox got two loud hits for their two runs in the top of the second. Bay led off by belting a solo shot to right-center. With two outs, Varitek smashed a towering drive over the right-field stands and on to Eutaw Street to make it 2-0.

In the midst of his most trying season offensively (.216, nine homers, 33 RBIs), Varitek keeps plugging away in hopes that something will click.

"It felt good," Varitek said of the homer. "It's been a fight every once in a while for one [successful] at-bat throughout a game, or one or two, so maybe it will start coming together."

Lester made that lead stand up until bottom of the fourth, when Aubrey Huff hit a fastball over the wall in center to make it 2-1.

From that point on, both starting pitchers got in a groove and stayed there.

Rocky Cherry came on for the Orioles in the eighth, and his night got off to an unfortunate start when Kevin Millar couldn't handle David Ortiz's hard grounder to first. The error came back to haunt the Orioles when Bay ripped Cherry's 81-mph slider high and far to make it 4-1.

In his first 16 games with the Red Sox, Bay is hitting .348 with three homers and 16 RBIs.

"With the guys in front of me, I get up there two or three times a game and there's guys on base," Bay said. "Part of my job is driving in runs. You have to have guys on base to do that. It's nice hitting fifth, just trying to be a complement to the puzzle. You're not asking one guy in that lineup to carry a load. You're asking a bunch of guys to pitch in. It's a lot easier to perform that way."

As it turns out, Bay's second homer was big. Manny Delcarmen walked two in the eighth. With two outs, Jonathan Papelbon came on and surrendered a two-run double to Huff, slimming the lead to 4-3.

The Red Sox bounced back with a couple of insurance runs in the ninth, giving Papelbon some security.

The closer nailed down a perfect ninth for save No. 33.