Combine the ground beef, bread crumbs, egg, milk, barbecue sauce, salt, pepper, and garlic powder in a bowl. Mix it well until it’s thoroughly combined.
Cut the top and bottom off of each onion, then cut them in half and peel off the outside “skin” layer. use the outside (largest) layers and set the inside layers aside.
Divide the ground beef mixture into 4 even parts and stuff it in between two outside onion layers, essentially stuffing each onion with meatloaf. Wrap each stuffed onion with 3-4 slices of bacon, securing the bacon ends with toothpicks.
Wrap each bomb in foil and place near the embers of the fire (or you can cook in a slow cooker) for 45 minutes to 1 hour, until ground beef is cooked through. Rotate them occasionally while cooking. Once they’re cooked through, baste with the additional barbecue sauce and cook for 5 more minutes to create the glaze.