Preheat oven to 375°F. Coat an 8-inch square (or 2-quart) deep baking dish with cooking spray.
Combine apples with granulated sugar (or Splenda), lemon juice and 1/2 teaspoon cinnamon in a large bowl. Toss to mix. Transfer to the prepared baking dish, cover with foil and bake for 30 minutes.
Meanwhile, combine whole-wheat flour, oats, brown sugar and the remaining 1/2 teaspoon cinnamon in a medium bowl. Mix to blend. Using your fingers (or a fork or pastry blender), cut in butter until evenly distributed and there are no chunks. Stir in oil, apple juice concentrate and nuts; toss well until evenly moistened and clumpy.
Remove the foil from the baking dish and scatter the topping evenly over the apples. Bake uncovered until the topping has browned and the fruit is soft and bubbling, about 30 minutes more. Let cool for at least 15 minutes before serving.