The most recent incident happened early this morning at the Denny's on South Shackleford Road.
Officers were called to the scene just before three o'clock.
A restaurant employee said shortly before the holdup, two men and two women had been sitting in the dining room waiting on food they had ordered, but then got up and left.
The employee said one of the men (described in the police report only as black) came back inside, pulled out a handgun, and threatened to shoot him before taking all the money from the cash register drawer. The man then got into a vehicle with the other three people and they drove away.
The other restaurant robbery happened a few miles away just hours before.
Officers were called to the Sonic on Stagecoach Road just before 11:30 Wednesday night.
In that incident, a worker told officers he was outside dumping the trash when two men with guns pushed him up against a fence. One of them then approached a car where another worker was sitting and made her get out.
The woman was ordered to go back into the restaurant, where the suspect told her to open the safe and took the money inside, before making her get inside a walk-in freezer.
After that, the second suspect then ordered the other worker back inside and also into the freezer before both suspects left the scene.
The incident report describes the suspects only as black men who were wearing dark clothing.