Place sweet potatoes in a large saucepan with enough water to cover. Bring to a boil, and cook until tender, about 15 minutes. Remove from heat, drain, and mash.
Place mashed sweet potatoes in large bowl, and use an electric mixer to blend with the margarine, brown sugar, orange juice, and cinnamon. Spread evenly into a 9x13 inch baking dish. Top with miniature marshmallows.
Bake for 25 to 30 minutes in the preheated oven, or until heated through, and marshmallows are puffed and golden brown.