Preheat oven to 375°.
Cut chiles in half lengthwise; discard seeds and membranes.
Combine cheese and next 9 ingredients (cheese through pepper) in a bowl; stir well. Divide vegetable mixture evenly among chile halves. Place stuffed chiles on a baking sheet coated with cooking spray. Bake at 375° for 20 minutes. Spoon 1 teaspoon yogurt onto each chile half.