Preheat the oven to 350°F, and grease two medium-large ramekins (or a loaf pan if you don't have ramekins) with coconut oil
To prepare the topping, whisk together the oats, flour, date sugar, and cinnamon in a small bowl. Cut in the coconut oil with a fork (or your hands) until a soft, crumbly mixture is achieved
To prepare the filling, toss the mixed berries with the cornstarch in a large bowl until completely coated.
Transfer the filling to the prepared ramekins or pan, and sprinkle evenly with the topping. I used smaller ramekins, so I pressed the topping on pretty firmly and placed the ramekins on a covered baking sheet to protect my oven from any dripping.
Bake at 350°F for 40 minutes or until the top is slightly crisp and you can see the juices bubbling at the sides of the dish.
Serve warm or cool.