PREHEAT oven to 400°F. Cut each potato lengthwise into eight wedges; place in large bowl. Add Italian dressing; toss to coat. Add 1/4 cup of the coating mix; toss to coat. Arrange on baking sheet sprayed with cooking spray. Bake 20 min.
MEANWHILE, spread remaining coating mix onto large plate. Spread tops of fish fillets evenly with half of the MIRACLE WHIP; press, dressing-sides down, into coating mix on plate. Repeat with remaining MIRACLE WHIP and coating mix on plate to coat remaining sides of fish fillets. Place on broiler pan.
BAKE potatoes an additional 15 min. and bake fish 15 min. or until fish flakes easily with fork and potatoes are tender.