Preheat oven to 425°.
Place oil in 9-inch cast-iron skillet; place pan in oven for 5 minutes.
While pan heats in oven, lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, cornmeal, and next 3 ingredients. Combine eggs and buttermilk, stirring with a whisk. Add to flour mixture, stirring just until moist. Stir in jalapeño peppers and cheese. Pour batter into preheated pan.
Bake at 425° for 20 to 23 minutes or until golden. Cut into 12 wedges.