Preheat oven to 375°.
Cut green chiles in half lengthwise. Arrange chiles in a single layer in an 8-inch square baking dish coated with cooking spray.
Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add turkey, onion, chili powder, cumin, salt, and garlic; sauté 5 minutes, stirring to crumble. Add diced tomatoes; cook 5 minutes or until liquid evaporates.
Spoon turkey mixture over chiles. Top with corn. Carefully spread beans over corn. Sprinkle cheese over beans. Bake at 375° for 30 minutes. Let stand 5 minutes; top with chopped tomato and green onions.