Heat oven to 400°F. Spray 11x7-inch (2-quart) glass baking dish with cooking spray.
In 12-inch nonstick skillet, heat 1 tablespoon of the oil over medium-high heat. Cook chicken, salt and pepper in oil 8 minutes, stirring occasionally, until chicken is no longer pink in center. Remove with slotted spoon to bowl. In same skillet, heat remaining 1 tablespoon oil over medium heat. Cook onion in oil 3 minutes, stirring occasionally, until tender. Add garlic and cumin; cook and stir 1 minute.
Return chicken to skillet, discarding any juices in bowl. Stir in beans, salsa and 2 tablespoons of the cilantro. Heat to boiling; remove from heat. Spoon into baking dish. Arrange sliced polenta over hot chicken mixture. Sprinkle evenly with cheeses and remaining 1 tablespoon cilantro.
Cover; bake 20 minutes. Uncover; bake 5 minutes longer or until thoroughly heated and cheese is melted.