Spray large skillet with nonstick cooking spray and heat over medium-high heat. Place one tortilla in skillet. On half of tortilla, add 4 apple slices, ¼ cup cheddar cheese, and 1 slice cooked bacon. Fold over tortilla. Cook 2-3 minutes, flip and cook additional 2-3 minutes, or until cheese is melted.
Place quesadilla on a cutting board and slice. Repeat with remaining tortillas