CARSON, Calif. -- Dwayne De Rosario scored the tiebreaking goal and had an assist to lead the Houston Dynamo to a playoff berth with a 3-1 victory against the Los Angeles Galaxy on Sunday night.

By extending their unbeaten streak to five games, the Dynamo (13-7-6) regained first place in the Western Conference by one point over Chivas USA. The victory, along with Columbus' loss on Saturday and Colorado's tie Sunday, made the Dynamo the first Western team to qualify for the 2007 MLS playoffs.

"It was a huge win for us," De Rosario said. "We all had one thing in mind and that was getting three points (for the victory)."

De Rosario broke a 1-1 tie by converting a penalty kick in the 47th minute. Galaxy defender Mike Randolph fouled Brian Mullan in the penalty area by pulling on his jersey.

"Obviously, the goal gives us energy and confidence, and we moved the ball better," Dynamo coach Dominic Kinnear said. "When we're passing the ball like that and have good mobility, it's hard to try and contain our attacking players."

De Rosario's header off Richard Mulrooney's corner kick enabled Ryan Cochrane to give Houston a 1-0 lead in the 21st minute with a 2-yard shot off the side of his left foot.

Los Angeles (4-13-5) tied it in the 26th minute on Alan Gordon's 10-yard header off Landon Donovan's corner kick.

Houston's Ricardo Clark ended the scoring in the 73rd minute with a 12-yard shot.

The loss ensured that the Galaxy would finish with their third losing season in five years.