Pour tomato sauce into a heavy-bottomed stock pot.
Turn the heat onto medium.
Slice mushrooms and add to tomato sauce.
Peel the entire head of garlic (yes, it’s a lot) and slice cloves fairly thickly. Add to sauce.
Dice onion and green bell pepper and add to sauce.
Add oregano and stir.
While sauce is simmering, brown ground beef. When no traces of pink remain, drain well and add to sauce.
Simmer for about 45-60 minutes, stirring often, until all vegetables are tender.
Serve over your favorite pasta and top with grated Parmesan cheese.