HEAT oven to 400°F.
TOSS potatoes with Italian dressing; spread onto bottom of 17x11-1/2x3/4-inch pan sprayed with cooking spray. Bake 15 min. Meanwhile, place 3 Tbsp. coating mix on plate. Spread fish with half the Miracle Whip; press, Miracle Whip-sides down, into coating mix. Repeat to coat other sides of fillets.
TURN potatoes. Place around edges of pan; sprinkle with remaining coating mix. Place fish in centre of pan.
BAKE 15 min. or until fish flakes easily with fork and potatoes are tender.