Preheat oven to 200°C.Add oats, banana, milk, peanut butter, maple syrup, baking powder and vanilla to a blender and blend until smooth.Spray an ovenproof dish with oil and pour in the oats mixture. Sprinkle over the mixed berries. Place dish on a baking tray and bake for 20 to 25 minutes.Remove from the oven and cut into four servings.TIP: You can also cook in individual ramekins.