Preheat oven to 350°F.

In a skillet, cook ground beef and onion over medium heat until meat is no longer pink; drain.

In a large bowl, mix together the cooked beef and onions, baked beans, ketchup, brown sugar, Worcestershire sauce, mustard, garlic powder, salt, and pepper.

Transfer the mixture to a greased baking dish.

Bake uncovered for 1 hour and 15 minutes, or until bubbly and heated through.