Brown the sausage slices in a skillet over medium heat until lightly colored on both sides. Drain any excess fat and transfer the sausage to the slow cooker.
Add the sliced bell peppers, onion, and minced garlic to the slow cooker.
Pour in the crushed tomatoes and beef broth.
Sprinkle in the Italian seasoning, salt, and black pepper. Stir gently to combine all ingredients.
Cover and cook on low for 6 hours or on high for 3 hours, until the peppers and onion are tender.
Stir once more before serving and top each bowl with the chopped parsley.