Combine meat, dry soup mix and egg in a large mixing bowl. Shape into 1-inch balls; place meatballs into slow cooker. Top with diced onions and KING'S HAWAIIAN Smoked Bacon BBQ Sauce; cover with lid.
Cook on LOW for 5 to 7 hours (or on HIGH for 2 to 3 hours). Gently stir to evenly coat meatballs with the sauce.
Place 1 bun half on each serving plate; top with 3 meatballs each.