Cut the celery and onion into small pieces.
Melt the margarine in a medium skillet. Add the celery and onion. Cook over medium to high heat until the margarine bubbles. Reduce the heat. Simmer until the onion is transparent. Set aside.
Cut the bread into quarters and place in a large bowl. Sprinkle with celery powder. Add the eggs and mix well using clean hands. Add the celery and onions and mix well.
Place in a greased loaf pan. Bake at 350 degrees for 45 minutes or until golden brown.