Set the top rack of the oven 6 inches from the broiler. Brush the peppers with vegetable oil, place on a sheet pan, and broil until blacked all over, turning every 2-3 minutes; this takes about 10 minutes. Place in a large mixing bowl, cover with a dinner plate or plastic wrap, and let sit for 15 minutes or until cool enough to handle. Turn off the broiler and set the oven to 375 degrees.

While the peppers are cooling, cook the quinoa in lightly salted water according to the package directions.

When the peppers are cooled, remove the skins and cut a slit down one side of the pepper and remove the seeds.

Heat the olive oil in a large skillet over medium-high heat. Add the onion and cook until softened, about 5 minutes. Add the cooked quinoa, beans, corn, salsa, and cumin and cook until heated through, about 5 minutes. Season to taste with salt and pepper.

Stuff the peppers with the quinoa mixture and place in a lightly oiled 9x12-inch baking dish. Cover with foil and bake for 15 minutes. Remove the foil, drizzle on the queso, and bake uncovered for 10 more minutes. Garnish with cilantro leaves and serve.