HEAT grill to medium-high heat.
SPOON 1/2 cup rice onto center of each of 4 large sheets of heavy-duty foil with sides slightly rolled up. Pour 1/2 cup warm water over each mound of rice; top with 1 fish fillet. Arrange spinach around fish; drizzle with dressing.
BRING up foil sides. Double fold top and ends to seal each packet, leaving room for heat circulation inside.
GRILL 10 min. or until fish flakes easily with fork. Cut slits in foil to release steam before opening packets; top with cheese.