Dice onion and mix with beef, uncooked rice, salt and pepper. Shape into meatballs.
In a large pan blend soup, water, and tomato sauce. Heat until mixture begins to simmer. Add meatballs. Bring to a boil, reduce heat and continue to simmer 30-40 minutes. Stir often.
Spray a separate skillet with cooking spray and heat over medium. Slice zucchini and mushrooms. Add to the skillet and saute until tender, about 7-8 minutes. Season with salt and top with Parmesan cheese.