Scrub potatoes well but do not peel.
Cut lengthwise into 1/4 inch thick slices and generously brush both sides with butter.
Sprinkle lightly with garlic salt.
Place on grill 4 to 6 inches above a solid bed of medium-glowing coals.
Cook, turning as needed to brown both sides, for about 30 minutes or until potatoes are soft when pierced.