2 tablespoons butter or vegetable oil
1 medium onion, peeled and diced
3 cups diced, cooked chicken
2 (14 1/2-ounce) cans green beans, drained and rinsed
1 (8-ounce) can water chestnuts, drained and chopped
1 (4-ounce) jar pimentos
1 (10 3/4-ounce) can condensed cream of celery soup
1 cup mayonnaise
1 (6-ounce) box long-grain wild rice, cooked according to package directions
1 cup grated sharp Cheddar
Preheat oven to 350 degrees F. Heat butter or oil in a small skillet over medium heat. Add onion and saute until translucent, about 5 minutes. Remove from heat and transfer to a large bowl. Add all remaining ingredients to bowl and mix together until thoroughly combined. Pour into a greased 3-quart casserole dish. Bake for 20 to 25 minutes or until bubbly. Let stand for a few minutes before serving.
*Make Ahead instructions: Prepare casserole, cover and freeze. Thaw in refrigerator then bake in refrigerator until bubbly.