Preheat the oven to 350 degrees. Prepare  a 9 x 14 x 2-inch oval baking dish with butter or baking spray. Set aside.

Peel the apples then core, and cut the apples into large wedges. In a large bowl combine the apples with the fresh orange zest, lemon zest, lemon juice, orange juice, sugar, cinnamon and nutmeg. Pour the apple mixture into the prepared dish.

To make the topping, in a medium mixing bowl combine the flour, brown sugar, granulated sugar, salt, oatmeal, and cold butter in the bowl of a stand mixer fitted with the paddle attachment. Mix on low speed until the mixture is crumbly and the butter is the size of peas. Or mix together with a pastry blender. Evenly distribute the crumb topping over the whole thing.

Place the baking pan on a sheet pan and bake for one hour until the top is brown and the apples are bubbly.

Serve warm and enjoy.