Preheat oven to 400°F and prepare a baking sheet lined with foil and a wire rack.
In a large bowl, combine ground beef, 2 tablespoons barbecue sauce, salt, and pepper gently to avoid tough burgers.
Divide beef mixture into 4 equal patties about 3 ½ inches in diameter and ½ inch thick.
Lay two bacon slices in a criss-cross (X) pattern on a tray or board. Place a burger patty on the bacon, then a pineapple slice on the patty.
Fold bacon slices over the burger and pineapple, securing with a toothpick at the crossing to hold them in place.
Place assembled burgers on the wire rack on the baking sheet; repeat for all burgers.
Bake for 15 minutes, then brush bacon with remaining 2 tablespoons barbecue sauce and continue baking 10-15 minutes until internal temperature reaches 160°F.
Toast burger buns while burgers finish cooking, if desired.
Remove burgers from oven and let rest 5 minutes before serving to redistribute juices.
Serve on buns as is or add preferred toppings like lettuce, onion, or cheese.