Toss the apples and rhubarb with sugar, 1/4 cup flour, cinnamon and apple pie spice.
Mix the flour, rolled oats, brown sugar, cinnamon, pecans, and melted butter in a medium bowl. Place apple mixture in an 8 x 8 inch baking dish. Sprinkle topping mixture on top.
Bake at 350º until bubbly and top is golden brown 35 to 45 minutes. Serve with Vanilla Ice Cream