Heat oven to 350°. Spray square baking dish, 8x8x2 inches, with cooking spray.
In medium bowl, pour water over bulgur. Let stand, stirring occasionally, 10 minutes or until water is absorbed. Stir in corn, 1/4 cup of the cheese, the jalapeño pepper, marjoram and garlic powder.
Slice chilies along one side; remove ribs and seeds. Drain well. Stuff about 1/4 cup filling into each chile. Place seam side down in baking dish. Top with salsa and remaining cheese.
Bake, uncovered, 25 to 30 minutes or until hot. Just before serving, spoon yogurt over chilies.