Preheat gas grill for medium heat. Meanwhile, stir together graham crackers, marshmallows, brownies and morsels in large bowl.
Place one 18x18 piece of heavy aluminum foil on counter. Spray with cooking spray. Place mixture in center of foil; drops dollops of peanut butter evenly over the top. Double fold top and ends of foil, leaving space for steam to gather.
Place packet on grate; cover grill. Grill 5 minutes or until marshmallows and morsels melt. Carefully open packet. Top with Reddi-wip® Original Dairy Whipped Topping, if desired. Serve immediately