Preheat the oven to 350. Spray a 9x13 baking dish with non stick cooking spray.
Toss the blueberries, raspberries and blackberriesin the baking dish.
In a mixing bowl, whisk together the remaining ingredients, except the brown sugar, cinnamon and nutmeg. Pour the batter over top of the fruit and stir gently to combine the fruit.
Sprinkle the brown sugar over the top. Then sprinkle the cinnamon and nutmeg over the top.
Bake in the preheated oven for 25 to 30 minutes, or until toothpick comes out clean in the middle.
Serve Triple BerryBaked Oatmeal with milk, cream, or yogurt for breakfast, or drop in a lunchbox, or for a fun weeknight 'brinner.'