Add cranberries, orange juice, water, zest and brown sugar to a pot set over medium heat. Stir well then once the cranberries start popping turn the heat down to medium low and cook for 12-15 minutes. Stir occassionally.
Smash any fully formed cranberries. Off the heat add the vanilla, stir and allow to thicken and cool to room temperature.
Preheat oven to 350 degrees.
Add flour, 3/4 c brown sugar, baking powder, kosher salt, cinnamon and oats to a large mixing bowl. Mix well then add the melted butter. Stir until everything is fully combined.
Place 2/3 of the crumble in a 9x9 parchment lined pan. Press the crumble into the bottom of the pan to create the crust. Bake for 10 minutes. Place the remaining crumble in the refrigerator while the crust bakes.
Pour the cranberry sauce on top of the warm crust and spread out evenly.
Break up the crumble topping with a fork if it hardened together. Top the cranberry layer with the crumble.
Finish with a sprinkle on top with the remaining 1/4 c brown sugar
Bake for 45 minutes on the middle rack.
Allow to cool for at least 4 hours before cutting.