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 in not impossible.
