Vegan Las Vegas!

Kristen Bell and Dax Shepard stepped out for lunch at LBS Burger at the Red Rock Resort & Spa in Las Vegas on Saturday.

The Hit and Run costars were also joined by Bell's parents.

"They were having a great time and were laughing together," an onlooker tells PEOPLE.

Bell and Shepard – who are vegan – both ordered the URTH burger, a house made vegan patty burger.

Bell paired her animal-free lunch with a side salad and water while Shepard snacked on waffle fries and a Diet Coke.
– Jennifer Garcia

Apparently Kristen Bell and Dax Shepard can't get enough of each other.

Aside from living together, Bell also stars in Hit & Run, a film directed and written by Shepard – and when they came out to a special screening of the movie on Wednesday at the Downtown Independent Theater, it was clear the engaged couple's flame has not died down.

During the Q & A for screening guests, "Dax lifted Kristen up and gave her a really affectionate kiss," an onlooker tells PEOPLE at the Brancott Estate Wines-hosted viewing. "At one point, Dax said to her, 'Shouldn't you be saying something really adorably cute right now? You're so good at that.' "

The source adds that Bell, who shared soda and popcorn with her fiancé until the screening started, told the audience having him as a boss was tough because, "If you think Dax Shepard the actor is cute, you wouldn't be able to handle it!"
– Dahvi Shira