Preheat oven to 350 degrees F.
Mash in the yams, butter, brown sugar, cinnamon and orange juice. Spread evenly in a large greased casserole or 9- x 13- inch pan.
Bake 20 minutes, remove from oven and top with marshmallows. Bake additional 5 to 10 minutes or until marshmallows are puffy and golden.
