Tejada and Lee each drove in four runs in a 12-5 victory Sunday, helping Roy Oswalt get his first win of the season.
Ivan Rodriguez had four hits for Houston, which set season highs for runs and hits (16) while completing a sweep of the three-game series. It was the Astros' first sweep since taking four from Pittsburgh last September.
Berkman missed his third straight game with a sprained left wrist but Tejada and Lee combined to go 12 for 23 with 12 RBIs against San Diego.
"Both of them have really swung the bat well for us," manager Cecil Cooper said. "Tejada started the season swinging it well and has continued. It's good to have them."
Tejada said each player on the team has to step up when Berkman is out.
"He's one of the best hitters in the league," Tejada said. "We knew we had to pick up the slack. We've got to play hard, everybody does, to make up for losing him."
Oswalt (1-2) gave up four runs and six hits in six innings. He ended a streak of five consecutive no-decisions, the longest of his career. He also stopped a stretch of seven starts without a win, which matched a career long that ran from September 2007 to April 2008.
"With Oswalt, you definitely know what you are going to get," said Chase Headley, who hit a two-run homer off Oswalt in the fourth. "He is going to throw you a lot of strikes. Today, we really didn't get a lot together off him."
Josh Geer (0-1) lasted only three-plus innings for San Diego. Geer, who played college ball at nearby Rice, gave up seven runs, five earned, and seven hits.
The Astros scored in three of the first four innings to build a 9-2 lead. Tejada hit a two-run homer in Houston's three-run first and drove in two more with a single in the second. Lee hit an RBI double in the fourth and Rodriguez tripled in a run.
"Those are two guys that are great offensive players and they have been major league All Stars," Padres manager Bud Black said of Tejada and Lee. "They have been producing all their careers and they are all hitting over .300 right now. They are experienced hitters and they know how to produce runs."
Lee and Rodriguez homered in the eighth to finish the scoring. Lee's two-run shot was his sixth of the season and Rodriguez's solo drive was his fourth.
Padres 2B David Eckstein left in the fifth inning with a bruised left rib. He was hit by a pitch from Oswalt in the fourth. The club said Eckstein is day to day. ... It was the first time Berkman has missed three straight games since May 15-17, 2006, when he was out with a sore left hamstring. ... Padres RHP Cha Seung Baek (strained right forearm) left a rehab appearance with Triple-A Portland with right elbow soreness. He will fly back to San Diego to be examined by team doctors. ... Since April 17, Padres starters are 0-9 with a 5.01 ERA in 22 games. San Diego is 6-16 in that span. A Padres starter has not won since Jake Peavy beat the Mets 6-5 on April 16 at New York. ... Houston re-signed INF Jason Smith and optioned RHP Jeff Fulchino to Triple-A Round Rock.