Boil 2 cups of water. Add a little salt, then quinoa. Stir, cover, and then simmer over low heat until the grains are tender and reveal their spiraled germ, about 15 minutes.
Preheat oven to 400 degrees. Warm half the oil in a skillet. Add scallions, and chiles, cook over medium heat for about 2 minutes. Add garlic, cumin, corn, and spinach, and 2 T. water. When the spinach is wilted, add the cilantro, quinoa, and Feta. Toss everything together. Season with salt and pepper to taste.
Slice peppers in half lengthwise without removing the tops or stems, then cut out the membranes and seeds. Microwave the cored pepper shells for about two minutes to soften them. They should be tender to the touch of a knife but not overly soft.
Fill the peppers with quinoa stuffing and place on a baking dish.
Drizzle the rest of the oil over the peppers and bake the peppers until heated through, 20 to 30 minutes, then switch the heat to broil and brown the tops. Serve hot, warm or at room temperature.