Preheat oven to 350 degrees. Place chicken in a lightly-oiled baking dish; top with onion, bell pepper and mushrooms.
In a medium bowl, combine next 7 ingredients (garlic through tomato sauce); pour mixture over chicken and veggies then sprinkle the cheese on top.
Bake for 35 to 45 minutes or until chicken juices run clear and cheese is bubbly and lightly browned. Serve immediately and enjoy!