1. Heat oil in large skillet over medium heat. Add onion; cook and stir 5 minutes or until tender. Layer 2 bread slices with onion, cheese and coleslaw; top with remaining 2 bread slices.
2. Heat same skillet over medium heat. Add sandwiches; press down with spatula or weigh down with small plate. Cook 4 to 5 minutes on each side or until cheese melts and sandwiches are browned.