PREHEAT greased grill to medium heat. Combine oranges, onions and cheese in medium bowl; set aside. Combine dressing and mint. Remove half of the dressing mixture; mix with the orange mixture. Reserve remaining dressing mixture for later use.
GRILL steak 5 to 6 min. on each side or until cooked to medium doneness (160°F), brushing frequently with the remaining dressing mixture.
CUT steak into thin strips; divide evenly among tortillas. Top with the orange mixture; roll up.