Renee Zellweger grabbed Bradley Cooper's butt during a trip to Barcelona.

The "Case 39" co-stars – who are rumored to be dating - flew to the Spanish city on Saturday (August 8, 2009) and onlookers claim they couldn't keep their hands off each other as they enjoyed several romantic dinners.

One said: "Bradley and Renee seem smitten with each other and at one point she cheekily grabbed his behind."

Renee and Bradley – who was recently linked to Jennifer Aniston – reportedly began dating last month after they were seen flirting during dinner at exclusive New York restaurant Antonucci.

An onlooker said: "He pulled her chair out for her when she sat down and he kissed her on the hand. If they're just friends, they were being awfully affectionate!"

"Throughout the meal they were playful and flirty. She played with her hair a lot, and she would often touch his arm when she was making a point about something."

"At one point, he seemed to want to whisper something to her as if it were a secret. He spoke into her ear and then they both started giggling."

Renee surprised her dinner companion by secretly paying the bill before he had a chance to.

The source added: "She told him she wanted to buy him dinner to pay him back for something. And when he opened the bill, it already had her card in it!"

Source: BANG Showbiz