Preheat oven to 350°F. Mix brown sugar and pumpkin pie spice in large bowl. Add sweet potatoes; toss well. Spread in 13x9-inch baking dish.
Mix orange juice and vanilla; pour over sweet potatoes. Dot with butter. Cover.
Bake 40 minutes. Remove from oven and stir. Bake, uncovered, 15 to 20 minutes longer or until sweet potatoes are fork tender.