Preheat the oven to 400 degrees F. Coat an 8 by 8-inch baking dish with cooking spray.
For the filling: In a large bowl, toss the berries with whole wheat flour, sugar and zest. Transfer the berry mixture to the baking dish and set aside.
For the topping: In a medium bowl whisk together the whole-wheat flour, all-purpose flour, 2 tablespoons of sugar, baking powder, baking soda and salt. Cut in the butter using 2 knives or a pastry cutter until many small pebble-sized pieces are formed.
In a small bowl or pitcher, whisk together the buttermilk and oil. Add the buttermilk-oil mixture to the dry ingredients and mix until just moistened. Do not over mix. Drop the batter onto the fruit forming 6 mounds. Sprinkle with the remaining teaspoon of sugar. Bake for 30 minutes, until fruit is bubbly and top is golden. Let stand for at least 10 minutes before serving.
Excellent source of: Vitamin C Good source of: Fiber, Manganese, Selenium