HEAT oven to 350ºF.
BROWN meat in large skillet; drain. Add onions; cook and stir on medium heat 2 min. or until crisp-tender. Add next 5 ingredients; mix well.
SPOON evenly into pepper halves; place in shallow baking dish. Pour water into bottom of dish; cover with foil.
BAKE 35 min. or until peppers are crisp-tender.