PREHEAT oven to 400°F. Add hot water to stuffing mix; stir just until moistened. Set aside.
COOK and stir sausage in large skillet on medium-high heat until evenly browned; drain. Add peppers and onions to skillet; cook until vegetables are crisp-tender, stirring occasionally. Spoon sausage mixture into 13x9-inch baking dish. Cover with tomato sauce and prepared stuffing.
BAKE 25 min. or until heated through.