Preheat oven to 350 degrees. Line a baking pan with parchment paper and set aside.

In a bowl combine oats, flour, crushed graham crackers, brown sugar and cinnamon. Pour melted butter and mix until everything is well incorporated and it resembles wet sand.

Measure ¾ cup of the mixture and reserve for the topping.

Press the rest into the prepared baking pan, pressing down firmly. Set aside.

In a bowl combine pumpkin puree with pumpkin pie spice and condensed milk. Pour over the pressed crust and top with the reserved crumb topping.

Take to the oven and bake for 30 minutes or until golden brown.

Let it cool completely before taking out of the pan and slicing.