Add onions; cook 5 min. or until crisp-tender, stirring frequently. Stir in garlic; cook 1 min.
Add water, potatoes and carrots; cover. Cook 10 min.; stir in zucchini. Cook, covered, 5 min. or until all vegetables are tender. Stir in tomato sauce and seasonings; simmer 3 min.
Spoon into chiles; place in shallow baking dish. Cover.
Bake 20 min. Top with cheese; bake; uncovered, 5 min. or until melted.