Preheat the oven to 375° F. Grease a 9 x 13 inch casserole dish with melted butter. Evenly layer the squash and apple slices in the casserole dish, alternating and slightly overlapping the squash slices with the apple slices, until all slices are gone. Drizzle the maple syrup over the squash and apples.
In a small bowl, mix together the brown sugar, flour, spices, salt and pepper. Mix the butter into the flour/sugar mix with your fingers to make a crumbly mixture. Sprinkle the mixture evenly over the top of the squash and apples. Cover the dish with foil and bake for about 40 minutes or until the squash and apples start to become tender. Remove the foil, and let casserole brown for another 15 minutes. Serve warm.