Preheat the oven to 350°. Pierce the potatoes all over with a knife, set them on the bottom rack of the oven and bake for about 1 hour, or until tender. Meanwhile, set the butternut squash, cut side down, on a lightly oiled baking pan. Cover with foil and bake on the upper rack of the oven for about 50 minutes, or until tender. Let the squash cool slightly, then peel and cut into 1-inch dice.