In a large bowl combine the potatoes and salad dressing mix. Spread half of the potatoes in a single layer on each prepared cookie sheet; lightly coat potatoes with cooking spray.
Bake in a 400 degrees F oven for 20 minutes; toss potatoes. Lightly coat potatoes again with cooking spray. Switch positions of cookie sheets in oven and bake about 20 minutes more or until potatoes are golden brown and crisp.