In a medium mixing bowl, combine onion, sour cream, Cream of Chicken soup, Cream of Celery soup, and chicken meat. Mix well. Pour into a greased 1 1/2 quart casserole.
Prepare Stove Top Stuffing mix according to package directions. Top casserole with stuffing.
Bake in 350 degree oven for approximately 30 minutes, or until bubbly.