The campaign -- which will debut this month in magazines and online -- was shot on Westward Beach in Malibu. The stars rocked out to a live Good Charlotte concert as photographer Larry Bartholomew took candid shots.
"When they asked if I wanted to be involved, I was like definitely!" said Madden, whose brother Benji made an appearance in one of the ads. "Op is a classic California skating and surfing brand. Its very cool for us. Its a natural, easy collaboration for Good Charlotte. We dont get to play a lot of shows on the beach so its cool to be here today playing on the beach for Op."
The spring and summer collection of Op is available exclusively at Wal-Mart.
"Its a fun shoot to get together with all these actors and entertainers and get to do something where we are having a good time and be in fun clothes," McCord said in a statement. "I love the pink bathing suit and the little T-shirts and shorts, they were my favorites from the shoot."
In addition to the campaign, the celebrities will host a launch party in California later this summer and make personal appearances on behalf of the brand.
"Being from California, I basically grew up wearing Op," Jenner said. "Its really cool for me to now be part of their new campaign."
This isn't the first time the brand -- whose chief marketing officer said is all about "good friends, good times and great casual clothing" -- has enlisted a large group of celebs for its advertising.
When the brand relaunched in 2008, Rumer Willis, Kristin Cavallari, Pete Wentz and Wilmer Valderrama were among the stars modeling the clothes.