1. Preheat oven to 350 degrees Fahrenheit.
2. Cut yams in half and boil until tender, but firm (about 20 minutes). When cool enough to handle, peel and slice into ¼-inch thickness.
3. Combine sugar, flour, salt, cinnamon, nutmeg, and grated orange peel.
4. Place half of sliced yams in medium-sized casserole dish. Sprinkle with spiced sugar mixture.
5. Dot with half the amount of margarine.
6. Add second layer of yams, using the rest of the ingredients in the order above. Add orange juice.
7. Bake uncovered for 20 minutes.