Preheat oven to 400 degrees F (200 degrees C). Grease a 9-inch square baking dish.
Mix cornmeal, flour, sugar, baking powder, and salt in a bowl. Beat eggs, milk, and oil together in a separate large bowl. Add cornmeal mixture to the egg mixture; mix until just combined. Fold blueberries into the batter; pour into the prepared baking dish.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 25 to 30 minutes.
