Preheat oven to 425°.
To prepare filling, heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add onion, bell pepper, garlic, and turkey; cook 5 minutes or until turkey loses its pink color. Add chili powder, oregano, 1/2 teaspoon salt, tomatoes, and beans; cook 3 minutes. Spoon turkey mixture into an 11 x 7-inch baking dish coated with cooking spray.
To prepare topping, lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, cornmeal, sugar, baking powder, 1/2 teaspoon salt, and baking soda in a bowl. Combine buttermilk and egg; add to dry ingredients, stirring just until moist. Spread cornmeal mixture evenly over turkey mixture. Bake at 425° for 18 minutes or until topping is golden.