Cut potatoes in half lengthwise; cut into 1/2-inch-thick slices.
Place potato slices, carrots, and squash in a lightly greased 13- x 9-inch baking dish.
Stir together sugar and next 6 ingredients. Drizzle over potato mixture, tossing to coat.
Bake, covered, at 425° for 30 minutes. Uncover and gently stir vegetables. Bake 15 or 20 more minutes or until vegetables are tender.