Preheat the oven to 350 degrees F. Spray the bottom of a glass or non-stick baking dish with nonstick spray. Wash and peel the sweet potatoes. Cut them into medium size pieces. Place the cut sweet potatoes in the baking dish and turn them so that they are coated with the oil. Bake for 60 minutes or until soft. Slice the cooked potatoes into bite-sized pieces and return them to the baking dish.
Sprinkle the potatoes with brown sugar and dot with butter. Cover the dish and bake for 15 minutes. Turn the oven to broil.
Remove the potatoes from the oven and sprinkle the marshmallows on top. Place under the broiler for a minute or two, just until the marshmallows turn light brown.
Notes
*If you are preparing this recipe as gluten-free, just be sure to use a brand of marshmallows that is known to be GF.