Preheat oven to 350°.
Lightly spoon flours into dry measuring cups; level with a knife. Combine flours, grits, sugar, salt, baking powder, and baking soda in a large bowl; make a well in center of mixture. Combine oil, banana, blueberries, and eggs; add to flour mixture. Stir just until moist.
Spoon batter into an 8 x 4-inch loaf pan coated with cooking spray. Bake at 350° 1 hour or until a wooden pick inserted in center comes out clean. Cool bread in pan 10 minutes on a wire rack. Remove bread from pan, and cool completely on wire rack.