Preheat oven to 400 degrees F (200 degrees C). Place the potatoes on a baking sheet, and bake 45 minutes, until cooked through and tender.

Place the squash in a pot with enough water to cover, and bring to a boil. Cook 10 minutes, or until tender. Transfer to a colander, and allow to drain for 30 minutes.

Cut the baked potatoes in half, and scoop out the pulp, taking care to leave skins intact. In a large bowl, mash together the potato pulp, squash, and butter. Spoon the mixture into the potato skins, and place on a baking sheet. Sprinkle with seasoned salt.

Reduce oven temperature to 350 degrees F (175 degrees C). Bake stuffed potato skins 30 minutes, until surface of filling is lightly browned.