Preheat oven to 375°.
Heat oil in a 10-inch cast-iron skillet over medium heat. Add onion, and sauté 5 minutes. Add 3/4 cup corn; sauté over medium-high heat 5 minutes or until lightly browned. Add oregano, cumin, and garlic; sauté 30 seconds. Add flour; cook 1 minute, stirring constantly. Add tomatoes, beans, and chiles, and cook 2 minutes or until thick. Remove from heat; spoon bean mixture into a bowl.
Spread 1/2 cup bean mixture over the bottom of skillet. Arrange half of tortilla quarters over bean mixture in skillet, overlapping slightly. Spread half of remaining bean mixture over tortilla quarters; sprinkle with green onions and 1/4 cup cilantro. Repeat with remaining tortillas and bean mixture. Top with 1/4 cup corn, cheese, and paprika.
Bake at 375° for 30 minutes or until thoroughly heated. Remove from oven; let stand 10 minutes. Spoon onto 4 plates; top with 1/4 cup cilantro, radishes, and sour cream.