Bring 2 quarts of water to a boil in a 3 quart saucepan. Place peppers in boiling water and boil for 10 minutes. Remove from water and set aside.
Heat olive oil in a 10-inch skillet over medium heat. Saute onions for 5 minutes. Add diced dates, garlic, corn, beans, ground cumin, dried oregano, chili powder, salt and pepper. Cook and stir for 5 minutes. Remove from heat.
Reserve 6 tablespoons cheese for topping. Add remaining cheese to the vegetable mixture. Stir to mix well.
Make a slit along the side of each pepper lengthwise, making sure not to cut the peppers in half. Scoop out the seeds and veins with a small spoon. Spoon one sixth of the mixture into each pepper. Place peppers in a 13 x 9-inch baking pan. Top each with 1 tablespoon of the reserved cheese. Bake for 15 minutes or until the filling is heated through and the cheese is melted. Serve immediately.