Preheat oven to 350º.
In a medium bowl, mix dry ingredients - flour, oats, spice, and sugar. Blend well.
In a small bowl, combine butter and apple sauce. Add to dry ingredients and mix until blended.
Press half of flour mixture into the bottom of a 9x13 pan. Leave the other half of the flour mixture in the bowl.
Peel, core, and slice the apples. Arrange about ⅓ of the apples on top of the flour mixture in the baking dish. Sprinkle with granulated sugar and pumpkin pie spice. Top with another ⅓ of the apples and more sugar and spice. Finish with the remaining apples, sugar, and spice.
Top apples with remaining flour mixture, and try to distribute it evenly across the apples.
Bake at 350 for 45 to 50 minutes, until apples are soft.