• Preheat your oven to 350°F. Line a 13x9-inch baking dish with parchment paper, leaving a 2-inch overhang on each side to easily lift the bars out, or lightly grease the dish with cooking spray.

For the crust and crumb topping:

• In a large mixing bowl, combine the butter, brown sugar, oats, flour, baking powder, salt, and cinnamon. Mix until the mixture is well blended and begins to clump together, with no large chunks of butter remaining. You can use a stand mixer with the paddle attachment or mix by hand. Set aside.

For the cranberry filling:

• Rinse and drain the cranberries. In a large bowl, combine the cranberries, sugar, cornstarch, orange zest, and orange juice. Stir until well mixed.
• Press 2/3 of the crumble mixture into the bottom of the prepared pan. Spread the cranberry mixture evenly over the crust, then sprinkle the remaining crumble over the top. For larger clumps, press the crumbs together or gently pat them down after sprinkling.
• Bake at 350°F for 45-50 minutes, or until the crust is golden brown and the filling is bubbling in the center, not just around the edges. If the crust is browning too quickly, cover the pan with foil. For the best results, chill in the refrigerator for 1 hours before icing and serving.

For the orange icing:

• In a small bowl, whisk together the powdered sugar, orange zest, and orange juice until smooth and at your desired consistency. For easy drizzling, transfer the icing to a zip-top bag, then snip a small corner and drizzle over the cooled bars. Alternatively, you can drizzle the icing directly with a spoon. To serve, use parchment paper to lift the bars out of the pan, then cut and enjoy.