In a large pot over medium heat, brown ground beef and Italian sausage. When meat is mostly done, add onion, green pepper and garlic; cook until slightly softened.
Add in tomato sauce, tomato paste, crushed tomatoes, oregano, Italian seasoning, vinegar, sugar (optional) and 1 cup water. Allow sauce to simmer while you prepare the cheese filling.
Stir together cottage cheese, 1 ½ cups mozzarella cheese and Parmesan cheese in a bowl.
Spray slow cooker lightly with cooking spray. Add 1 ½ cups sauce to bottom of slow cooker, then layer 3-4 lasagna noodles on top, ⅓ of the cheese mixture and 1 cup sauce. Repeat layers twice more.
Top with remaining sauce, and sprinkle ½ cup mozzarella cheese on top.
Cover and cook on low 3-4 hours.
Notes
We recommend using a good quality tomato sauce here, such as Muir Glen. This sauce can be used as the base of other pasta recipes as well.