Preheat oven to 350~. Pam 1 lg, 2 med, or 3 sm loaf pans. Sift the dry ingredients (flour, cornmeal, soda, baking powder, and salt) together into a large bowl. Combine the blueberries, walnuts, and oats in a second bowl, and sprinkle 1 tablespoon of the flour mixture over them. In a third bowl, beat together the oil, eggs, buttermilk, sugar, and lemon rind. Quickly combine dry and wet mixtures, using as few strokes as possible. Gently stir in the berries. Batter should be stiff. Spoon batter into prepared pan/ pans. Bake 45 to 55 minutes (large pans), 35 to 50 (medium), and 35 to 40 (small). Check 2/3 of the way through the baking period; if loaves are browning excessively, tent loosely with foil. Let baked breads cool 10 minutes in pan, run knife around the edge of pan, and turn loaves out. Let finish cooling on a rack. Yield 1 large, 2 medium, or 3 mini loaves.