Heat olive oil in a large skillet over medium-high heat. Add the Italian sausage (or ground beef or turkey) and cook, crumbling the meat, for 3-4 minutes. Add the onion and continue cooking until sausage is cooked through. Add the minced garlic and cook for 1 more minute, stirring. Drain off excess grease.
1 tablespoon olive oil, 1 pound Italian sausage, 1 small onion, 4 cloves garlic
Transfer meat mixture to slow cooker. Add the crushed tomatoes, diced tomatoes, Italian seasoning, oregano, basil, salt, pepper and water. Stir. (Do not add the pasta yet; it cooks at the very end. Don't worry that the mixture will seem liquidy right now. The extra water will be absorbed later on when the pasta cooks in the slow cooker.)
28 ounce can crushed tomatoes, 15 ounce can diced tomatoes, 1 ½ teaspoons Italian seasoning, 1 teaspoon dried oregano, 1 teaspoon dried basil, ¾ teaspoon salt, ⅛ teaspoon black pepper, 2 ½ cups water
Cover and cook on high setting for about 3 hours or low setting for about 6 hours.
Stir in the pasta, pressing it all down into the liquid. Cover and continue cooking on HIGH for 15-25 minutes, stirring it once after 15 minutes to make sure pasta cooks evenly. (Pasta cook time will vary by slow cooker. If you’ve had your slow cooker on the low setting, it will take longer to cook the pasta when you switch to the high setting.)
16 ounces uncooked ziti pasta
When pasta is tender, turn off the slow cooker.
Sprinkle the shredded mozzarella over the top of the pasta. Cover and let rest for 5 minutes until cheese on top is melted. Then serve.
1 cup (4 ounces) shredded mozzarella cheese