Brown beef with onion, zucchini and mushrooms.
Put beef/veggie mixture in slow cooker with tomato sauce, stewed tomatoes and seasonings. Mix well.
Cover and cook on low for 6-8 hours.
30 minutes before serving, add in cheese, stir and continue cooking.
Serve over traditional pasta, zucchini noodles (zoodles) or spaghetti squash.