Preheat grill to high. Divide the meat into 4 equal portions. Form each portion loosely into a ¾-inch burger and make a deep depression in the center with your thumb.

Brush each burger with oil and season with salt and pepper on both sides.

Place the burger directly on the grill, until slightly charred on both sides and cooked to desired doneness. Add 2 slices of cheese to each burger during the last minute of cooking. Close the lid to melt the cheese.

Place a tablespoon of BBQ sauce on the top and bottom of the toasted buns. Place the burgers onto the buns. Top each with bacon, onion rings, and top bun.