Preheat oven to 400F. Line 12-cup muffin pan with muffin papers. Whisk buttermilk, eggs and corn oil together in small bowl. Sift cornmeal, flour, brown sugar, baking powder, baking soda and salt into large bowl. Add blueberries and toss to coat thoroughly. Add buttermilk mixture and stir just until dry ingredients are moist.

Spoon batter into prepared muffin pan. Bake until tester inserted into center of muffins comes out clean, about 27 minutes. Transfer muffins to rack. Let stand 15 minutes and serve.