Preheat oven to 350º F. Spray an 8x8 baking pan or large pie plate with nonstick cooking spray. Set aside.
Cream together butter and sugar until light and fluffy, about 3 minutes. Add in egg, vanilla, salt, all-purpose flour and oats. Mix just until well-combined. Stir in grated apple and apple pie spice. Spread into prepared baking pan.
Bake 20-25 minutes until set in the middle and lightly golden brown. Cool on a rack until completely cooled before cutting into pieces.