Preheat oven to 400 and spray 13 x 9 glass baking dish.
Combine chicken, artichoke hearts, water chestnuts, mushrooms, chicken soup, sour cream and mayonnaise in a large bowl. Transfer into prepared dish and sprinkle with onion rings (can use nuts, bacon, crumbled Ritz or soda crackers, or toasted white bread crumbs instead).
Bake until it is bubbling (if using nuts they will be toasted) about 35 minutes. Serve while hot - Can serve over wild rice!