01 -
Preheat oven to 175°C (350°F). Grease a 9×13 inch baking dish or line with parchment paper for easier removal.
02 -
In a large bowl, combine flour, rolled oats, brown sugar, granulated sugar, baking powder, baking soda, salt, cinnamon, and nutmeg. Stir until well incorporated.
03 -
Pour melted butter into the dry mixture and mix until crumbly. Reserve 1 cup of this mixture for the topping.
04 -
In a medium bowl, whisk together pumpkin puree, sweetened condensed milk, vanilla extract, and egg until smooth and well combined.
05 -
Press the remaining crumble mixture firmly into the prepared baking dish. Bake for 15 minutes until light golden brown.
06 -
Pour the pumpkin filling over the pre-baked crust, spreading evenly with a spatula. Sprinkle the reserved crumble mixture on top. Add chopped pecans if using.
07 -
Bake for 25-30 minutes until the top is golden and the filling is set. Cool completely on a wire rack before cutting into bars.
08 -
Dust with powdered sugar before serving if desired.