Gyllenhaal, 30, and a group of friends (including Maroon 5 singer Adam Levine) spent the evening at the Spare Room in L.A. bowling and drinking Red Stripe beer.
"They looked really into it and seemed really relaxed," a witness tells UsMagazine.com. "As the game progressed, the guys started high-fiving each other; at one point Jake did what looked like a little dance after bowling a spare."
Witherspoon, 35, and Gyllenhaal met on the set of 2007's Rendition and dated until late 2009. Just a few months later in February 2010, the Legally Blonde actress was spotted out with future husband Toth. Still Gyllenhaal, who's been single since his brief relationship with Taylor Swift ended in January, didn't seem to be sweating Witherspoon's wedding. In fact the he even managed to chat up a few ladies at the lanes.
First Gyllenhaal joked with a brunette. "They seemed very comfortable together but not really romantic," says the witness.
And around 1 in the morning, he logged some time with Sweedish model Mini Anden, 32.
"He put his hand on her back, trying to convince her to bowl with them and being really sweet," says the witness. "He looked like he was trying to give her a lesson on bowling. He seemed to want to show off a little bit."