Joined by another female friend, the pair stepped out for brunch at BLD in West Hollywood on Saturday.
"They were very low-key and sat in the center of the restaurant, pretty much unnoticed by fellow diners," an onlooker tells PEOPLE.
Both of the famous friends were dressed down – Moore wore her hair in a bun and a gray V-neck T-shirt, while Minka sported a cozy gray sweater with her hair down in waves – and "didn't have a stitch of makeup on," the source adds.
While deep in conversation, Moore sipped on iced tea while the table shared granola, fruit, sandwiches and salads.
– Melody Chiu