For topping, stir together brown sugar, rolled oats, 1/2 cup of the flour, and the 3 tablespoons granulated sugar in a medium mixing bowl. Using a pastry blender, cut in butter until the mixture resembles coarse crumbs. Stir in almonds.
For filling, stir together remaining flour, the 1/3 cup granulated sugar, the cinnamon, nutmeg, and ginger in a large mixing bowl. Add the peach slices and peach nectar or orange juice. Toss gently to coat.
Transfer filling to an ungreased 3-quart rectangular baking dish. Sprinkle topping over the filling. Bake in preheated oven for 30 to 35 minutes or until fruit slices are tender and the topping is golden. Serve warm or at room temperature with ice cream.