HEAT barbecue to medium-high heat.
CUT fish into 4 pieces. Place 1 fish piece on centre of each of 4 large sheets heavy-duty foil sprayed with cooking spray. Spoon vegetables over fish.
BRING up foil sides. Double fold top and ends to seal each packet, leaving room for heat circulation inside.
GRILL 8 to 10 min. or until fish flakes easily with fork and vegetables are crisp-tender. Cut slits in foil to release steam before opening packets. Drizzle 1 Tbsp. dressing over each serving.