I've worked in a lot of restaurants over the years (at least 7), though not since about 1984, and with the exception of Pizza Hut, not one ever gave the employees free food.
Mark
My favorite restaurant gives their employees half-off all their meals. Result: Employees hang out there a lot even when they aren't working. Of course, when they only pay you $2.13 an hour plus tips, they may be eating there more out of necessity than desire. Most of their employees are college-aged.