Preheat the oven to 350°F and have a 8"x8" pan ready.
Mix together all of the filling ingredients until well combined in the baking dish. Spread out evenly.
To make the topping, stir together the oat flour, oats, brown sugar, salt, and baking powder until combined. Cut in the butter with a fork or your hands until the topping is crumbly.
Sprinkle the topping evenly over the filling. Place the crisp in the oven and bake for 40-45 minutes, or until the topping is browned and the filling is bubbly.