The O.C. alum, 32, wore a grey, draped skirt, white tank top, and charcoal cardigan with shades and gladiator sandals.
Bilson is expecting her first child with longtime boyfriend Hayden Christensen, and her growing baby bump was on full display during the outing.
"Her best friend has a kid, and she has a lot of friends with children, so I'm just there to support her however I can and honor and respect her processes," Bilson's Hart of Dixie star Jamie King told Us Weekly in May. "She loves James, she's always bringing him toys. Just seeing her with my son, I know she's going to be the best mother."