Divide the ground beef into 4 equal portions and form into 4 patties. Set aside.
Prepare pub sauce:
In a small mixing bowl, combine the mayonnaise, ketchup and mustard. Mix until all are well blended. Add the relish and season to taste with salt and pepper.
Grill the burgers to your preferred doneness. During the last minute or so of cooking, place 2 slices of Cooper cheese on each burger and cook until the cheese is nice and melty.
Assemble your burgers:
Open the kaiser rolls. Add your desired amount of pub sauce to the bottom sections of the rolls. Place one cheeseburger patty on the bottom of each roll. Top each burger with the baby greens, pickles, red onion slices, and tomato. Cap off each burger with the top sections of the seeded rolls.