Preheat oven to 350 degrees.
In a large skillet, saute onion and celery in butter until softened.
Stir in rice, rice seasoning packet, cream of chicken soup and chicken broth; mix well.
Pour into a 13x9-inch baking dish. Place chicken tenderloins in casserole and try to cover chicken with rice mixture.
Bake 45 - 50 minutes until rice is tender and most liquid is absorbed.
Let stand 5 minutes before serving.