Preheat oven to 350 degrees F. Cook rice according to pkg. directions. Brown ground beef in iron skillet. Add salt and pepper to taste. Save meat juice. Remove meat with slotted spoon. Add meat to rice. (1/2 rice-1/2 meat)
Saute celery (and onion if using) in meat juice. Remove with slotted spoon and add to rice and meat mixture.
Add mushroom soup and rice mixture to 8" square oven dish, casserole dish, mixing well.