1Heat gas or charcoal grill. Spray 1 (18x18-inch) sheet of heavy-duty foil with cooking spray. Place potatoes on center of foil. Drizzle with dressing; mix gently. Sprinkle with cheese blend.
2Bring up 2 sides of foil over potatoes so edges meet. Seal edges, making tight 1/2-inch fold; fold again, allowing space for heat circulation and expansion. Fold other sides to seal.
3Place packet on grill over medium heat. Cover grill; cook 20 to 25 minutes, rotating packet occasionally, until potatoes are tender. Place packet on serving platter. Cut large X across top of packet; carefully fold back foil. Sprinkle with Parmesan cheese.