Gently toss together blackberries, raspberries, blueberries and white sugar in a bowl; set aside.
In a separate bowl, combine flour, oats, brown sugar, cinnamon and nutmeg. Rub in the butter until crumbly. Press half of mixture in the bottom of a baking dish. Cover with berries. Sprinkle the remaining crumble mixture over the berries.
Bake in the preheated oven for 30 to 40 minutes, or until fruit is bubbly and topping is golden brown.
I exchanged the blackberrys for strawberrys. It tasted really nice and was quick and easy to make. The berrys could be suplimented with any fruits easily enough. Thank's for sharing this recipe, I'll be making it again. - 15 Aug 2011