Cook the bacon and set aside.
Season burgers with salt, pepper and garlic powder.
Grill, pan-fry, or broil burgers, about 4 minutes on each side. Top with cheese and cook for about 1 more minute.
Meanwhile, heat oil and butter in a large skillet over medium-high heat. Add onions and peppers and sprinkle with salt and pepper.
Cook, stirring every few minutes, until onions are caramelized and peppers are slightly browned, about 10 minutes.
Lightly toast the buns and place lettuce on each, drizzle with ketchup, top with cheeseburger, caramelized onions and peppers and finally bacon!