Stir turkey, eggs, 1/2 of the onion, bread crumbs, 1/2 cup Parmesan cheese, parsley, garlic, oregano, salt and pepper in a large bowl until well blended. Roll turkey mixture into balls using 1 tablespoon per meatball.
Add meatballs and remaining ingredients, except pasta and spinach to slow cooker crock.
Cover slow cooker and cook on HIGH for 3 to 3 1/2 hours or LOW for 6 to 6 1/2. Add pasta, cover and continue cooking for 15 minutes until pasta is tender and meatballs are cooked through.
Stir in spinach and remaining Parmesan cheese before serving. Garnish with Parmesan cheese and coarse black pepper.