Preheat oven to 450º.
Combine cornmeal, 1/2 teaspoon salt, black pepper, and red pepper in a shallow dish; set aside.
Combine buttermilk and egg in a large bowl, stirring with a whisk. Add okra; toss to coat. Let stand 3 minutes.
Dredge okra in cornmeal mixture. Place okra on a jelly-roll pan coated with cooking spray. Lightly coat okra with cooking spray. Bake at 450º for 40 minutes, stirring once. Sprinkle with remaining 1/4 teaspoon salt.