In medium skillet, cook bacon and onion over medium heat until bacon is crisp and onion is tender, stirring frequently.
Meanwhile, in medium bowl, combine ground beef, 2 tablespoons of the barbecue sauce, seasoned salt and pepper; mix well. Shape mixture into 4 patties, 1/2 inch thick.
With slotted spoon, remove bacon-onion mixture from skillet; cover to keep warm. Add patties to same skillet; cook over medium heat for 10 to 12 minutes or until thoroughly cooked, turning once.
Spread remaining 2 tablespoons barbecue sauce on bottom halves of buns. Top each with burger, bacon-onion mixture and top half of bun.