Add all-purpose flour, granulated sugar, and baking powder to a medium mixing bowl. Whisk to combine.
Using a pastry blender, cut in the cold butter until crumbly in texture.
Divide the mixture into 2 parts, 2/3 + 1/3. Press 2/3 of the mixture into the bottom of the prepared pan. Use a small offset spatula to ensure the mixture is evenly spread across the bottom of the prepared pan.
Pour the blueberry mixture over the crumble layer in the baking pan.
Add light brown sugar and granulated sugar to remaining crumble mixture.
Sprinkle the remaining crumble mixture over the blueberry filling.
Bake in preheated oven for 45 to 50 minutes or until the blueberry filling is bubbly and the crumble topping is golden brown.
Remove from oven and place pan on wire rack. Cool to room temperature.
Lift the bars from the baking pan using the parchment paper overhang. Slice into individual bars.