Preheat and prepare grill to indirect heat. Add 3-4 wood chips to the coals when coals are ready.
For the Topping: Cut butter into small cubes then place in freezer while other ingredients are being prepared.
In a large bowl, mix together all of the topping ingredients (except butter). When butter is very cold add it to the mix and cut the butter into the mix using a fork (could also use a stand mixer for this, but it works fine with your hands and a fork). Mix together until the mix is crumbly and the butter resembles the size of peas.
Transfer the topping mix to the freezer until ready to pour over the filling.
For the Filling: In another large bowl, mix together all filling ingredients. Transfer to your baking dish (remember this is for four portions, so we used a smaller dish. 10x5x2 inch oval cast iron pan works well (approx 1 qt capacity). You can find the exact pan we used below in notes.
Sprinkle the apple filling with the topping mixture and cover with foil.
Cook: Place on grill on indirect heat for 15 minutes. Remove foil, and then continue cooking on the grill for an additional 15 minutes, or until the mixture is bubbly and topping is crispy. Add wood chips as you see the flame die down, every 15 minutes or so for a handful of wood chips.
Serve warm with a big scoop of vanilla ice cream.