HEAT large skillet sprayed with cooking spray on medium heat. Add vegetables; cook and stir 2 to 3 min. or until crisp-tender.
BRUSH pizza sauce onto half the tortilla; cover with 1 cheese slice, pepperoni, cooked vegetables and olives. Top with remaining cheese slice. Fold tortilla in half.
WIPE skillet with paper towel; spray with additional cooking spray. Add quesadilla to skillet; cook 3 to 4 min. or until cheese is melted and quesadilla is golden brown on both sides, turning after 2 min.