1Heat oven to 350º. Butter 3-quart casserole. Cook noodles as directed on package, except cook 2 minutes less than package directions.
2While noodles are cooking, heat oil in 10-inch skillet over medium-high heat. Cook onion and celery in oil about 5 minutes, stirring occasionally, until tender. Stir in remaining ingredients.
3Drain noodles; place in casserole. Top with chicken mixture. Cover and bake 30 minutes; stir. Bake uncovered about 15 minutes longer or until liquid is absorbed.