Crockpot Spaghetti Sauce

1 large onion chopped
2 tbsp. vegetable oil
2 lbs ground beef (cooked and drained)
½ pound ground sausage (cooked and drained)
16 cups chopped tomatoes (pureed)
4 small cans of mushrooms
1 1/2 teaspoons minced garlic
2 tablespoons dried oregano
2 tablespoons dried basil
2 bay leaves
1/4 cup chopped parsley
1/4 cup white sugar
3 tablespoons salt
3/4 teaspoon ground black pepper
2 (6 ounce) cans tomato paste

Sauté chopped onions in vegetable oil until tender. Mix all ingredients in crockpot and simmer until desired thickness (6-7 hours on high, 8-10 hours on low). Stir occasionally during the day. Remove bay leaves prior to eating/freezing.