Start by making a foil packet from 2 layers of aluminum foil about 20" x 30" If using the narrower 12" foil use 4 sheets 12" x 30" and seam 2 sheets to the other 2 sheets length wise with a triple fold 1" wide seam.
Wash & slice potatoes about 3/8" thick with skins on. Peel onions and slice about 1/4" thick. Spray upside of foil with cooking spray. Place potatoes & onions in the center of foil sheets cover with small pats of butter and salt & pepper to taste. Pull up short sides and triple fold to form a 1" seam. Roll up and crimp closed the remaining open sides. Shake side to side a little make potatoes & onions into an even layer. Cook over medium heat turning often 20-25 minutes or until potatoes are done. You can move to the top rack of your grill to keep hot until ready to serve. Serves 4 to 6 people
This makes a very easy side dish for your cookout that everyone will love and can be made a little bit ahead of time. If you get rained out these can also be cooked in the oven. This side dish does not travel very well but it is not impossible.
