Peel and slice potatoes.  Line cookie sheet with foil.  Spray foil with nonstick spray.  In large bowl, combine potatoes, green onions, green peppers and white onions.  Pour onto foil lined pan.  In same bowl, mix barbecue sauce, water and dry spices.  Pour over top of potatoes.  Bake in 400° oven for 45 minutes.  Turn and separate to ensure even cooking.  Bake an additional 10 minutes.  Baking time depends on how thick you slice the potatoes.  Sprinkle grated cheese on top of cooked potatoes, and continue cooking until cheese has melted and the edges become crispy.  Let sit for about 4 to 5 minutes before serving to allow the cheese to set up a bit.