The third baseman backhanded Melvin Mora's sharp grounder with the bases loaded and threw to first baseman Kevin Youkilis for the final out, bailing out struggling closer Jonathan Papelbon and preserving Boston's 11-9 win over Baltimore on Sunday.
"I felt good once I caught it because that was the hardest part," Lowell said. "I was glad Youk squeezed it because the inning was a pain."
The ninth began with the Red Sox leading 11-7 and ended with them one game off the AL East lead held by New York. The Yankees visit Fenway Park for a five-game series, starting with a day-night doubleheader Friday.
The Red Sox are 11-1 this season against Baltimore. Boston swept the series following a road trip in which it lost the last five games.
"We just swept the Orioles. How can I have a bad taste in my mouth?" Papelbon said. "It's just one of those games where you have to keep grinding and just find a way to get through it."
Boston's Manny Ramirez went 0-for-3, including a liner that shortstop Miguel Tejada dove to catch, and had his hitting streak end at 27 games. He might've been credited with a single on a grounder to pitcher Todd Williams but jogged down the line and was safe when Williams made a wild throw for an error.
"He asked me, 'If I ran do you think they'd give me a hit on that?"' Lowell said. "I said, 'I don't know. You didn't run, so don't worry about it."
Lowell's first grand slam of the season gave Boston a 4-1 lead in the first, but the Orioles kept coming back. Papelbon, who had blown his two previous save opportunities, got his 31st save in 36 chances after the Orioles scored twice in the ninth, on an error by shortstop Alex Cora and a bases-loaded walk to Brian Roberts.
Then Lowell stabbed Mora's sharp grounder.
"Great play by Mike Lowell," said former Boston first baseman Kevin Millar, who hit one of Baltimore's three homers. "That play was a tough play down the line and he made it look easy. It was a couple inches away from making it a game."
Jon Lester (6-2) allowed four runs in five innings and won for the first time in five starts.
Daniel Cabrera (5-8) gave up seven runs in four innings and is 1-1 since being recalled from Triple-A Ottawa last Tuesday.
"He was a little tentative," Baltimore manager Sam Perlozzo said. "I don't think his velocity ever reached to where it usually is."
Lowell's fifth career slam was the major-league high 10th allowed by the Orioles this season. They gave up 28 runs in the series.
"I think that pretty much summarizes it," Perlozzo said.
Youkilis' three-run homer put Boston ahead 10-6 in the seventh, and Doug Mirabelli hit his sixth of the season and third in three games in the eighth.
"Doug's home run might be overlooked, but it was big," Boston manager Terry Francona said. "We desperately needed to win these three games."
David Ortiz, topping the majors in RBI and tied for the home run lead, sat out his second game of the season to rest before a three-game series against AL Central-leading Detroit and the big set with the Yankees.
Corey Patterson, Millar and Roberts homered for Baltimore.
The Orioles led 1-0 in the first on a sacrifice fly by Tejada after Roberts doubled and stole third. The Red Sox struck for four runs in the bottom half when Lowell homered after Mark Loretta walked, Youkilis doubled and Ramirez walked.
Baltimore tied it at four in the second. Ramon Hernandez led off with a walk and scored on Patterson's 12th homer. Nick Markakis then doubled and scored on Mora's single.
The Red Sox went ahead 7-4 with three runs in the fourth when they loaded the bases on a single by Wily Mo Pena, a walk to Lowell and a bunt single by Cora. One run scored on Gabe Kapler's groundout, another on Cabrera's wild pitch and a third on Coco Crisp's single.
Kyle Snyder replaced Lester to start the sixth and, on his first pitch, gave up Millar's ninth homer. Two batters later, Roberts hit his fourth to make it 7-6.
Youkilis gave the Red Sox a cushion with his homer off Williams after Crisp walked and Loretta was hit by a pitch. Mora's RBI single made it 10-7 in the eighth.
"The whole game was a grind," Youkilis said.
- Ramirez's hitting streak was the second-longest in the majors this year behind Chase Utley's 35-game streak for Philadelphia. It was Boston's longest since Johnny Damon hit safely in 29 consecutive games last year.
- The Red Sox signed RHP Bryan Corey to a minor league contract with Triple-A Pawtucket. Boston obtained him from Texas on July 30 and designated him for assignment on Aug. 5. He then was granted free agency.
- Boston is 15-1 against the Orioles beginning last Sept. 3 after going 14-18 against them before that.