Preheat your oven to 375. Toss all of the filling ingredients together in a bowl and transfer to a 7.5x10.5 inch casserole dish.
Add all of the topping ingredients into a food processor and pulse a few times until a chunky granola-like consistency is formed. Alternatively, to avoid using a food processor, you can finely chop the nuts and add them to a bowl and mix with the remaining topping ingredients.
Spread the topping evenly over the berry mixture. Bake for 30 minutes or until the sides are bubbling and the topping is lightly browned. Enjoy with a scoop of ice cream of choice!
Video
Notes
*I tried making this with frozen berries and it worked, but it was very liquidy. Fresh berries are preferred!