In a large mixing bowl, combine ground beef, barbecue sauce, garlic powder, black pepper, and salt. Mix well using your hands.
Take a small handful of the mixture (about 1/4 pound) and shape it into a thin patty. Repeat this process to make a total of 12 patties.
Lay the patties out on a cookie sheet and cover them with plastic wrap. Place the patties in the refrigerator.
In a large skillet, cook the bacon over medium-high heat, turning occasionally, until it is evenly browned. This should take about 5 minutes.
Use a slotted spoon to remove the bacon from the skillet. Drain the bacon on paper towels.
Reduce the heat to medium and cook the onions in the remaining bacon drippings until they are soft and just beginning to brown.
In a small bowl, mix the cooked onions and bacon together.
Preheat an outdoor grill to medium heat and lightly oil the grate.
Take the beef patties out of the refrigerator. On 6 of the patties, place 1-1/2 tablespoons of the bacon and onion mixture, and sprinkle them with shredded cheese.
Top each of the filled patties with one of the remaining patties. Press the edges together to seal them.
Grill the stuffed patties until the beef is no longer pink in the center. This should take about 4