Heat oven to 375°F. Coat two 8-1/2 x 4-1/2 x 2-5/8-inch loaf pans with nonstick cooking spray.
In a large bowl, whisk flour, cornmeal, sugar, baking powder, salt and baking soda until blended. Make a well in flour mixture. Whisk buttermilk, oil, eggs and vanilla in a measuring cup; add to flour mixture. Gently whisk just until ingredients are moistened. Fold in blueberries.
Divide batter evenly among prepared loaf pans. (This batter can also be made into muffins; baking time will decrease slightly.)
Bake at 375°F for 25 to 30 minutes until lightly crowned and lightly browned. Let cool in pans on rack 5 minutes. Turn out onto rack; let cool.
