Combine first 5 ingredients in a large bowl; make a well in center of mixture. Combine buttermilk and next 3 ingredients; stir in corn, green onions, jalapeño pepper, and garlic. Add to dry ingredients, stirring just until moistened.
Spoon batter into a 9-inch square pan coated with cooking spray. Bake at 375° for 30 to 35 minutes or until done. Cool 5 minutes in pan on a wire rack.