Preheat oven to 350°F; grease a 9x13 inch baking dish with non-stick cooking spray.
In a large bowl, combine chicken, onion, water chestnuts, green beans, pimientos, cream of celery soup, mayonnaise, and the cooked wild rice blend. Mix all ingredients together until well combined.
Transfer the mixture to greased baking dish; spread it out evenly. Sprinkle the grated cheddar cheese over the top of the casserole.
Bake in preheated oven for 30 minutes, until cheese is melted and bubbly.
Enjoy your delicious Paula Deen's Chicken and Rice Casserole!