Combine first 7 ingredients in a large bowl; stir in half of French fried onion rings. Spoon casserole mixture into a lightly greased 2- or 3-quart slow cooker.
Cover and cook on LOW 2 hours. Sprinkle remaining onion rings on top of casserole. Cover and cook on LOW 30 more minutes.
* Roasted turkey
* Garlic mashed potatoes
* Cranberry sauce