Police said a group of people entered the fast food chain's Palm Beach store about 2.50am on Sunday and started causing a disturbance.
A security guard who approached the group was set upon by three men, one of whom grabbed the guard's torch and struck him on the head.
He was taken to Gold Coast Hospital with head injuries.
A second guard who intervened suffered lacerations and a hand injury.
The offenders all fled on foot.
One was last seen wearing a black hooded jumper, beige shorts, dark shoes and a maroon cap.
Another had on a black hooded jumper with white stripes on the selves, black shorts with white stripes and dark shoes, while the third culprit was dressed in a white t-shirt, black shorts and brown shoes.
Anyone with information should call Crime Stoppers on 1800 333 000.
