Heat oven to 450 degrees F. Lightly moisten pork tenderloin with water; coat with seasoned coating mix. Set aside while preparing vegetables. Discard any remaining coating mix.

Meanwhile, in large bowl combine sweet potatoes, onion and dressing; toss to coat. Spread vegetables in 9 x 13-inch baking pan. Place pork on top of vegetables. Roast for 20 minutes or until meat thermometer inserted in center of pork reads 155 degrees F., stirring vegetables once. Remove from oven. Let stand for 5 minutes. Slice pork; serve with vegetables, sprinkled with chopped parsley, if desired.