Step 1
Combine mince, breadcrumbs, egg, onion and 1 tablespoon sauce in a large bowl. Shape mixture into four 2cm-thick patties.
Step 2
Heat a greased barbecue plate and chargrill on medium-high. Cook patties on plate for 4 to 5 minutes each side or until cooked.
Step 3
Meanwhile, cook bacon and pineapple with patties on barbecue plate for 1 to 2 minutes each side or until browned. Spray cut sides of buns with oil. Cook on chargrill for 2 minutes each side or until browned.
Step 4
Spread bun bases with mayonnaise. Top with lettuce, pineapple, patties, cheese and bacon. Drizzle with remaining barbecue sauce. Sandwich with bun tops. Serve.