"It's the best we've been and we need to continue that. We need to continue to grind out these games," manager Joe Girardi said. "It has been very professional the way these guys have gone about their business. Every day you come in and expect to win."
The Yankees (57-37) woke up alone in first place Wednesday, the first time that's happened this late in a season since they won the division in 2006.
They played as though they plan to stay there.
Jorge Posada homered and drove in two runs, Alex Rodriguez had an RBI single and Mariano Rivera earned his fifth save in six days. The AL East leaders scored four times in the first inning and sent rookie Jason Berken (1-8) to his eighth loss in a row.
The Yankees are 6-0 since the All-Star break after opening 8-0 in the second half last year. They've won 19 of 26 to move 20 games over .500 for the first time since finishing 94-68 in 2007 and have opened a season-high, two-game lead over second-place Boston in the AL East.
New York is poised to extend the surge, too. Next up, a four-game series against another last-place team (Oakland) to conclude this 10-game homestand.
"I think we're right where we need to be," Swisher said. "We're all feeling really good right now."
Swisher capped the early outburst with a two-run single and made three fine plays in right field, making up for a third-inning error. Baltimore botched a key defensive play, when second baseman Brian Roberts mishandled Robinson Cano's RBI infield single with two outs in the first.
Adam Jones, the Orioles' lone All-Star, homered and had four hits. He and Nick Markakis connected for consecutive solo shots with two outs in the ninth off Brian Bruney, prompting Girardi to call on Rivera.
The 39-year-old closer threw a called third strike past Aubrey Huff to convert his 24th consecutive save and 28th in 29 chances this season.
"Personal success has its place, but I'd rather have won the series," Jones said. "Some of the mistakes we made, they're not making. They've definitely turned their season around from the first month."
Derek Jeter got New York started with a leadoff double, and Posada's RBI double in the eighth made it 6-2. It appeared the four-run cushion would provide Rivera with a well-deserved rest, but Bruney couldn't close it out after fanning his first two hitters.
Burnett (9-4) took a four-hit shutout into the seventh, improving to 9-1 in 11 career starts against Baltimore. The right-hander is 4-0 in his past five outings overall and 7-2 with a 2.31 ERA in his last 10.
Converted starter Phil Hughes, emerging as a reliable setup man, worked a scoreless eighth that included a strikeout and a double-play grounder.
"He's been very good," Posada said. "Finding him to do that setup role is the reason why we're here."
Baltimore stranded seven runners through the first four innings and lost its 10th straight in the Bronx. The Orioles dropped to 1-14 in road games against division opponents this year and 2-25 dating to last season.
Making his first start against the Yankees, Berken fell to 0-8 in 10 outings since beating Toronto 7-2 in his major league debut May 26.
"After that first inning, things went well and that was a step in the right direction," he said.
Swisher missed Roberts' fly ball for a two-base error to start the third. But with runners at second and third, Burnett struck out Huff before Swisher ran down Ty Wigginton's drive into the right-field corner.
The fun-loving Swisher, adorned with tattoos and a semi-mohawk, scaled the wall with his spikes after making the grab. Appreciative of the effort, Burnett pointed to him with both hands.
"I was just happy as hell I caught it," Swisher said. "I just think with every win that we get, the fun is building up and building up."
Swisher also held Luke Scott to a second-inning single on a shot off the wall and mini-jumped at the fence to catch Scott's drive in the sixth.
Orioles manager Dave Trembley said he'll probably speak Friday in Boston with president of baseball operations Andy MacPhail before deciding whether to remove struggling left-hander Rich Hill from the rotation. ... The Yankees are 26-9 at home since Rodriguez returned from hip surgery.