Lightly butter each bun and set aside.
Form each 2 ounce portion beef into thin (bun sized) patties and generously season all sides with salt and pepper.
Turn grill on medium-high(~400˚F) and brush grates with oil.
Once grill is hot, place beef patties onto grill and sear for 2 to 3 minutes.
Flip patties and sear on other side for 2 to 3 minutes.
Top each patty with a slice of American cheese and close grill lid for 1 minute.
Remove patties from grill, stacking half the patties onto the other half of patties (so you have 4 stacks with 2 patties each) and transfer to a platter. Scrape grill grates clean.
Place buns onto grill, buttered side down, and grill for 30 seconds. Remove from grill and set aside.
To assemble: Stack each burger bun with bbq sauce, two patties with cheese, 4 slices of crispy cooked bacon, 2 to 3 onion rings, more bbq sauce, and the tops of each burger bun. Serve.