Cut six 12x12 inch sheets of foil and spray with non-stick spray. Peel 3 potatoes and cut two thick cuts from center. Place on foil. Slice remainder of potato thinner. Slice large onion, spread on top of potatoes.

Slice squash and spread on top of onion. Slice green squash and place on top. Spread any remaining potato.

Put large pat of butter on top of vegetables. Salt to taste. Fold and seal. Place on grill for 30 minutes.