The 25-year-old sported a halter-neck black dress with cream patterns and chunky black heels, while Laura opted for a floor-length cornflower blue dress and wore her blonde hair in loose waves.
Cressida (centre) with Joanne Froggatt and Laura Carmichael (right)
Joanne, who attended the event with her husband of two years James Cannon, wowed in a metallic dress with hexagonal prints.
The North Yorkshire-born actress is nominated for the Golden Globes' Best Supporting Actress in TV and will no doubt be cheered on by her IT director husband at the ceremony on Sunday night.
Joanne, who plays Anna in Downton, and her husband James
The Out of Towners dinner at Chateau Marmont also attracted stars including James Corden, James Nesbitt, Dominic West, Camilla Belle, Gillian Anderson and Freddie Fox.
Cressida wasn't the only British socialite at the soiree. Poppy Delevingne was in attendance with her husband James Cook.
Charlotte Tilbury, the make-up artist behind Poppy's stunning wedding day look,