The Red Sox’ Jason Bay, right, celebrates his two-run home run with David Ortiz during last night’s eighth inning.

AP / Nick Wass

BALTIMORE — The Red Sox made history the last time they played a series at Oriole Park at Camden Yards.

Actually, it wasn’t a team effort that made it into the record books — it was former Red Sox slugger Manny Ramirez who made headlines when he hit his 500th career home run against the Orioles.

A lot has happened since May 31.

Ramirez is gone via trade after he soured on his Boston teammates and his Boston teammates soured on him. The Sox’ clubhouse was in some sort of disarray with an unhappy Ramirez around, so management did something about it and traded him as part of a three-team deal with Los Angeles and Pittsburgh.

Boston’s new left fielder became Jason Bay, and he helped his new teammates beat the Orioles last night, 6-3.

Bay slugged two home runs — a solo shot in the second and a two-run blast in the eighth — to help Boston to victory. He finished with four RBI. He wasn’t alone in the home run department, however, as Jason Varitek hit a round-tripper, too.

Bay “had four RBI, and the two home runs speak for themselves,” Sox manager Terry Francona said. “We needed it.”

It wasn’t all offense that helped the Sox snap a two-game losing streak. Starter Jon Lester was outstanding in his seven-inning outing, in which he allowed only one run — a solo homer to the Orioles’ Aubrey Huff — on four hits with one walk and five strikeouts. He improved to 12-4.

Bay has hit safely in 14 of 16 games since joining the Red Sox.

“It’s easy to say you’re going to come in and not replace someone, or not stress,” said Bay. “Getting off to a rough start, as much as you want to say wouldn’t be a big deal, it definitely doesn’t help. So coming in and being as consistent as I have as allowed me to be myself and not struggle and not try to do too much. It has allowed me to stay even-keeled and that’s something I pride myself on. (Sunday) was a bad day, but (last night) was a good one.”

After a 0-for-3 performance at Fenway Park on Sunday, Bay hit a solo home run in the top of the second inning last night to give Boston a 1-0 lead. He drove a 2-1 offering from Orioles starter Jeremy Guthrie into the right-center-field seats, about 400 feet from home plate.

While Bay’s homer — his second with the Red Sox since he was acquired from Pittsburgh at the trade deadline late last month — wasn’t a surprise, Varitek’s was. Boston’s captain has been struggling at the plate this season, and he entered last night’s game with a .164 average in his last 11 games. During batting practice yesterday afternoon, Varitek was crushing the ball, and he carried that into his first at-bat in the second inning.

With two outs, he demolished a 2-0 offering from Guthrie, hitting it onto the walkway behind the right-field wall. For Varitek, a switch-hitter, it was his first home run from the left side of the plate since May 21.

So Boston held a 2-0 advantage as Lester continued to deal.

The only run he allowed was Huff’s solo homer, in the bottom of the fourth inning. As soon as Huff made contact with Lester’s offering, the Sox pitcher immediately knew it was gone. Huff’s shot landed just over the center-field wall and was estimated at 412 feet.

With Guthrie out of the game after seven innings, Boston tagged Baltimore reliever Rocky Cherry for a pair of runs in the top of the eighth when Bay provided his second homer of the game, a two-run shot to deep center. It was the 12th time in Bay’s career that he recorded a multiple-homer game. His last two-homer game came on July 12 at St. Louis while with the Pirates.

“Everybody knows he’s a good hitter,” said David Ortiz, a close friend of Ramirez’s. “Everybody expects that from him.”

Boston’s held a 4-1 lead until the bottom of the eighth.

With Lester done after seven strong innings, reliever Manny Delcarmen allowed two runs as Baltimore narrowed its deficit to 4-3. The Sox’ hard-throwing right-hander quickly recorded two outs before he issued back-to-back walks and was lifted in favor of closer Jonathan Papelbon.

Papelbon surrendered a two-run double to Huff, which was the first hit Papelbon had allowed in the eighth inning this season. Fortunately for the Red Sox, he got Ramon Hernandez to end the inning, leaving the potential tying run on second base.

Boston added some insurance in the top of the ninth. Dustin Pedroia legged out an infield dribbler and scored from first when David Ortiz doubled to left-center field.

Ortiz moved to third when Kevin Youkilis grounded out to second. Ortiz then scored on fielder’s choice when Baltimore’s Alex Cintron decided to throw home on Bay’s grounder to short. Everyone was safe and Boston had a 6-3 advantage.

With a three-run cushion, Papelbon easily recorded his 33rd save of the season.

At the time of the trade, Bay said he didn’t want to replace anyone, he just wanted to be himself and help the Red Sox win.

And he did so in a big way last night.

“It’s been a little refreshing for me to be consistent,” said Bay. “Because of that it’s easy to just keep doing what you’re doing.”

jmcdonal@projo.com