1. Cook bacon in a skillet over medium heat until crisp; drain.
2. Place beef in a medium bowl. Drizzle with oil, and sprinkle with garlic powder, pepper, and salt; mix well to combine. Divide mixture into 8 equal portions, shaping each into a 3-inch patty.
3. Heat a grill pan or cast-iron skillet over medium-high heat. Coat pan with cooking spray. Add patties; cook 3 minutes or until seared. Turn patties over; top each with 1 piece of cheese. Cover and cook 2 additional minutes or until beef is done and cheese melts.
4. Spread 1 teaspoon ketchup on top half of each bun; top each with 1/2 teaspoon onion. Layer bottom half of bun with 1 lettuce leaf, 1 patty, 1 bacon piece, and top half of bun.