Preheat oven to 350°. In a nonstick skillet coated lightly with oil, brown chicken over medium heat. Transfer to a 13x9-in. baking dish coated with cooking spray., Recoat skillet with oil. Add onion; cook and stir over medium heat until tender. Stir in remaining ingredients; bring to a boil. Reduce heat; simmer, uncovered, 15 minutes. Pour over chicken. , Bake, uncovered, until a thermometer inserted in chicken reads 170°, 35-45 minutes.