Scarlett Johansson didn't just celebrate July 4 over the long weekend -- she feted fiance Romain Dauriac for his birthday, too.

The parents-to-be and four friends had a celebratory dinner at Indian Wells Tavern in Amagansett on Thursday night. Johansson, 29, concealed her baby bump in a tee and black overalls and ordered a turkey burger and club soda, a spy told us.

The group sang "Happy Birthday" to the French journalist before digging into chocolate peanut butter pie.