I'm not a fan of using tin foil on my grill or in my oven purely for the clean up factor. Inevitably every time I use foil it manages to tear and make a bigger mess than was intended to begin with. Grill Magic came up with this three pack of barbecue mats to avoid situations exactly like that.
Each mat is super thin and lets the right amount of heat through. They easily wash up and store in tubular form to avoid creases and damage. The mats work by allowing enough heat through the mat that the food cooks, but not too much heat to destroy the mat all together. While these are mostly recommended for the barbecue I found they work nicely for cookies in the oven as well. Creates an awesome non-stick surface for almost any type of cooking.