Preheat your oven to 350. In a large bowl, combine all the ingredients for the oat mixture. Press 2/3 of the mixture into a baking sheet (I use a 9×11) and pack it down to form a crust. Bake for 15 minutes.
In a medium sized mixing bowl combine all the ingredients for the berry mix. Pour this mixture over the oat crust and top with remaining oat mixture.
Bake for 30 minutes. Allow to cool and set for at least 30 minutes before serving with vanilla ice cream!
You can use any combination of berries for this recipe. If you want to use all blueberries, all raspberries, or even blackberries, go for it!