Preheat oven to 350 degrees. In a 10 inch ovenproof skillet or 8 inch square baking dish, layer sliced nectarines. Top nectarines with minced basil and sprinkle the Cointreau over the nectarines.  Combine oats, brown sugar, cinnamon and flour in a mixing bowl.   Dice butter into small pieces and cut into the flour mixture with either two forks or a pastry blender.  Combine until butter and flour mixture is coarse crumbs.  Sprinkle the crumb topping evenly over the nectarines.  Bake 40 - 45 minutes.  Serves 6.