Add the cranberry sauce and sugar to a small skillet set over medium heat. Whisk to combine then cook, stirring often, for 3-5 minutes- just until the sugar's dissolved. Remove from heat and set aside.
1 cup cranberry sauce, 1/4 cup sugar
To a mixing bowl add the oats, flour, brown sugar, and salt. Stir everything together until evenly combined.
1 cup flour, 1 cup old fashioned rolled oats, 3/4 packed cup brown sugar, 1/4 tsp salt
Add the butter to the mixing bowl and cut in using a pastry blender until evenly incorporated and the mixture's crumbly.
1 stick butter
Spray a 9x9" square baking dish with with nonstick cooking spray. Add 2 cups of the streusel topping to the dish and press out in an even layer.
Add the cranberry sauce and spread out in an even layer overtop. Sprinkle the remaining streusel mixture evenly overtop.
Bake at 350° for 30-35 minutes, until the crust's lightly browned.
Remove the dish from the oven and let it cool completely.
Slice into squares, serve, and enjoy!