Preheat grill to medium heat.
Combine ground turkey breast, garlic powder, Italian herb seasoning, pineapple and 1 tablespoon barbecue sauce in a medium bowl; mix well. Form into 4 patties, approximately 5-inches in diameter. Set aside.
Slice red onion into 1/4-inch thick slices. Toss onions with oil. Grill onions until tender and caramelized using a grill pan; about 10 to 12 minutes.
Place turkey burgers on grill grates sprayed with grilling spray. Grill over direct heat for 5 minutes; turn apply 1 tablespoon barbecue sauce to top of the burger. Continue grilling an additional 7 to 10 minutes or until internal temperature reaches 165ºF.
Toast buns for 2 minutes while onions and patties are grilling; remove, set aside.
Place cooked burger on bottom bun. Place an equal amount of onions and barbecue sauce on each burger . Add lettuce and tomato, if desired, and top with top half of bun.