It may be the holiday season, but Jessica Simpson and Dallas Cowboys quarterback Tony Romo — her beau since mid-November — seemed more in the mood for Valentine's Day at pal CaCee Cobb's 30th birthday bash at Hollywood hot spot Teddy's on December 1.

"They were all over each other on the couch, making out," a Simpson source tells Us Weekly in its new issue, on newsstands now.

"They were on top of each other! It was a little bit much for a public place," the witness adds. "He was holding her close and she wasn't paying attention to anyone else."

The source adds that Simpson, 27, is "crazy" about her man, also 27, "and gushes about how sweet he is."

Apparently, he's also generous too: Simpson, who split from Nick Lachey two years ago, was overheard that night telling pal Ken Paves that Romo (who recently signed a $67.5 million contract with the Cowboys) picked up the Teddy's check for their entire 12-person party!