• Preheat the oven to 350℉. Line an 8x8 pan with parchment paper; set aside.

Streusel Topping

• In a medium-sized mixing bowl, mix the oats, brown sugar, spices and flour together. Add cold butter that has been cut into small cubes or grated with a box grater.
• Work the cold butter into the mixture with a pastry blender or fork until you have coarse crumbs. Set aside in the refrigerator until needed.

Shortbread Crust

• Whisk the flour, sugar, salt and cinnamon in a medium-sized bowl.
• Melt the butter in a saucepan or in the microwave. Add melted butter and vanilla to dry ingredients; mix together to form a dough.
• Press the dough evenly into the bottom of a lined 8x8 baking pan and bake at 350℉ for 10-12 minutes or until lightly browned.

Apple Pie Filling

• Peel, core and slice the apples into thin, even slices (about ¼” thick).
• In a large bowl, mix the flour, sugar and spices together. Add the sliced apples and coat evenly. Set aside until the crust is done baking.

Apple Pie Bar Assembly

• Remove the crust from the oven when done baking.
• Carefully spread the apple pie filling over the hot crust in an even layer until completely covered. Next, remove the streusel from the refrigerator and completely cover the apple pie filling.
• Bake at 350℉ for 30-35 minutes or until the streusel is golden brown.
• Remove from the oven and cool for 30 minutes on a cooling rack. Transfer bars to the refrigerator and chill for an additional hour before cutting into bars. Depending on how you cut the bars, you will get 9 to 12 slices.
• Bars can be enjoyed cold, warmed or at room temperature. Store in the refrigerator for up to 5 days.