Cut the stems out of the peppers, then cut the peppers in half. Set aside.
In a large skillet, saute the onion in the olive oil over medium heat for a couple minutes to soften. Then add the ground beef and cook until no longer pink. Add the corn, black beans, and taco seasoning to the skillet. Simmer for a few minutes, stirring occasionally. Divide the taco mixture among the 6 pepper halves.
Pour 1/4 cup water in a 9 x 13 inch baking dish. Add the stuffed peppers to the dish, then cover with foil. Bake for 25 to 30 minutes, or until peppers are beginning to get tender. Remove the foil and add the cheese to the peppers. Bake for another 3 to 5 minutes to melt the cheese. Garnish with cilantro and serve warm.