Halladay (10-3) improved to 30-3 in a Philadelphia uniform in the 35 starts in which the Phillies have given him the lead.
"Obviously pitching with the lead is always beneficial for a pitcher," Halladay said.
For Halladay, though, it's almost a guaranteed victory.
"He's pretty steady," Philadelphia manager Charlie Manuel said. "If we can score three or four runs, our starting pitchers have a good chance to win the game. We scratched out three runs and he did a tremendous job. It might not sound like a lot of runs but it gives him room to work."
Halladay gave up eight hits and walked none in tying for the major league high in victories. He struck out four, raising his NL-topping total to 123. The Phillies have won each of Halladay's last eight starts and the right-hander is 5-0 with a 2.64 ERA during the stretch.
"It's always fun to watch him pitch," Philadelphia slugger Ryan Howard said. "He's a competitor."
But, obviously, he's not fun to hit against. Even on a day when the A's managed eight hits, Halladay kept Oakland to just one run.
"Yeah, he obviously pitched well," said Oakland's Scott Sizemore, who went 1 for 3. "We got quite a few hits off him. We weren't able to piece them together. I guess that's why he's so good. He spreads them out and bears down when he needs to."
The number of hits allowed didn't bother Halladay, who said he was hitting his spots.
"I felt like for the most part we were making pitches and giving up hits on good pitches," he said.
The Phillies also got a boost from Rollins, who entered 0 for 8 before two solid singles, an infield single and a double on Sunday.
"Jimmy's had some good games," Manuel said. "His consistency at times hasn't been real good. He's due to get in a good streak. Usually he'll hit a period where he's very consistent and hopefully today might help him get into one. His swing has been real good at times. Today he was very good against the lefty."
The Phillies are off Monday before hosting the Boston Red Sox for three games in what many are billing as a possible World Series preview.
Josh Outman (3-2), a former Phillies minor leaguer, allowed three runs and eight hits in six innings. He was picked by the Phillies in the 10th round of the 2005 draft and traded to Oakland in 2008 as part of the deal for Joe Blanton.
"He started a little slow but from the third inning on, he pitched a lot better," Oakland manager Bob Melvin said.
The Phillies started the game with three straight hits off Outman. Rollins singled, Polanco doubled, Shane Victorino hit an RBI single and Howard had a double-play groundout that scored a run for a 2-0 lead.
The Phillies got that run back in the fifth on Ben Francisco's two-out infield single with the bases loaded.
"To be able to add on, that's the important thing," Halladay said. "It's sometimes tough to pitch in a one-run game, so not always pitching with the tying run at the plate ... those extra runs make a big difference."
Outman cleanly fielded Francisco's slowly hit roller to the left of the pitcher's mound and looked to third to try to get Polanco, but third baseman Sizemore was charging and not on the bag. By the time Outman turned and fired to first, it was too late to get Francisco.
The A's threatened in the seventh when Jackson led off with a single and, after an out, went to third on Sizemore's double down the right-field line. Jackson may have scored on the hit, but he appeared to hesitate rounding second. Oakland couldn't get the run home as Landon Powell popped out and pinch-hitter David DeJesus struck out looking. DeJesus has three hits in his last 38 at-bats (.079).
"When he needs to make that big pitch, he does," Sizemore said. "He's pretty tough to beat."
Philadelphia right fielder Domonic Brown, booed for failing to run out a grounder in Saturday's game, was not in the lineup on Sunday. Brown, who Manuel said afterward was slated for the day off, was replaced by Francisco.
Manuel, however, could've elected to play Francisco in left field and sat slumping left-handed hitting Raul Ibanez, who entered 4 for 35 with no RBIs in his last 10 games. Ibanez, who hasn't homered in his last 23 games, went 1 for 4.
Howard went 0 for 2 and is hitless in his last nine at-bats. But he stole his first base of the season in the seventh. ... Cliff Pennington went 0 for 4 for Oakland and is now hitless in his last 19 at-bats. ... Outman went 0 for 2, dropping A's pitchers to 0 for 18 this season. ... The Phillies recorded their 166th consecutive sellout and second-largest regular-season crowd with 45,863 fans.