In a large bowl, combine the cornmeal, flour, sugar, baking powder, salt and baking soda. In a small bowl, whisk the eggs, milk and oil. Stir into dry ingredients just until moistened. Fold in corn and onion.
Pour into a greased 13-in. x 9-in. baking dish. Bake at 400° for 25-30 minutes or until toothpick inserted near the center comes out clean. Serve warm. Yield: 12-15 servings.