Cook patties and onions in hot oil in large skillet on medium heat 10 to 12 min. or until patties are done, turning patties after 6 min. and stirring onions frequently.
Cut patties in half. Spoon onions onto bottom halves of rolls; cover with patties and cheese.
Broil, 6 inches from heat, 1 min. or until cheese is melted. Cover with tops of rolls.