Preheat the oven to 375°F. Line an 8-inch square baking pan with parchment paper.
In a large bowl, whisk together the flour, oats, sugar, cinnamon and baking powder with 1/2 teaspoon kosher salt.
Add the melted butter and vanilla extract to the flour mixture and stir until the butter is incorporated and the dough begins to clump together.
Press two-thirds of the crumble mixture into the bottom of the prepared baking pan, spreading it into an even layer.
Bake the base layer for 10 minutes then remove it from the oven.
Spoon the leftover cranberry sauce on top of the base then spread it into an even layer. (The cranberry sauce will sink slightly into the base since it is warm.)
Spinkle pieces of the remaining crumble mixture on top. Bake the bars until the top crumble mixture is golden and set, 25 to 30 minutes.
Remove the bars from the oven and let them cool completely in the pan before slicing and serving. (See Kelly’s Note.)