In a large skillet saute onion in butter or margarine until tender. Remove from heat. Add the bread crumbs, apples, celery, parsley and salt. Mix all together. Cut a large pocket in the side of each pork chop; season inside and out with salt and pepper to taste. Spoon apple mixture loosely into pockets.
In skillet, heat oil to medium high and brown chops on both sides. Place browned chops in an ungreased 9x13 inch baking dish. Cover with aluminum foil and bake in the preheated oven for 30 minutes. Remove cover and bake for 30 minutes longer or until juices run clear.