Roy Oswalt officially has accepted his proposed trade to the Philadelphia Phillies.

After considering his options and speaking with friends familiar with the Phillies' situation, including former teammate Brad Lidge, the Houston Astros' staff ace waived his no-trade clause Thursday in order to be dealt for left-handed starter J.A. Happ and two prospects, outfielder Anthony Gose and shortstop Jonathan Villar.

"I'm glad it worked out for both of us. I wanted to go to a contender, and Houston gets some good prospects in return who will hopefully allow them to build a winning team," Oswalt told ESPN.com's Amy K. Nelson.

"The hardest part about it is cleaning out my locker. I've been in the same place for 10 years and having to say goodbye and clean out the locker is the toughest part," he said.

Astros general manager Ed Wade saluted Oswalt for his time in Houston.

"We salute what Roy did for the organization and the contributions that he made here over the course of his career in an Astros uniform and his profile here is significant," Wade said. "At the end of the day, we have to do what's best for the Houston Astros. You can't make a deal like this as a favor to a player. In this case I think we served everybody's purposes with what we did."

Oswalt, who was previously scheduled to start Friday against the Brewers, said he will fly to Washington on Thursday night and start for the Phillies Friday against the Nationals. Coincidentally, Happ was scheduled to start Friday for the Phillies.

The Phillies, who had won seven straight and were 3½ games behind the NL East-leading Atlanta Braves entering Thursday's games, get one of baseball's best right-handers and a pitcher with playoff experience.

"We're trying to do what we can to get back to the World Series and win it," Phillies general manager Ruben Amaro Jr. said. "To have Roy Oswalt, Roy Halladay and additionally Cole Hamels, Joe Blanton and Kyle Kendrick, we stack ourselves up as one of the best rotations in baseball."