In a small pot, bring the quinoa and vegetable broth to a boil over high heat. Reduce the heat to low, cover the pot, and let it simmer until the liquid is absorbed (usually 12-15 minutes.) Let it cool down and then fluff it by stirring it.
Preheat the oven to 375°F (190°C). Lightly grease a medium-sized sheet pan or 9x13 casserole dish. Spread 1/2 tbsp of oil onto the peppers. Sprinkle a little salt and pepper onto them and roast them for 10 minutes.
Meanwhile, heat the remaining oil in a small skillet over medium-high heat. Add the onion and sauté it for 5 minutes. Stir in the seasoning and garlic. Cook this for 1-2 minutes as it becomes fragrant, then take it off the heat.
Add the sautéed onion mixture to the quinoa along with the black beans, tomatoes, green chilies, corn, and half of the cheese. Stir everything together.
Stuff the peppers with the filling. Top them with the remaining vegan cheese and bake them for 20 minutes or until the peppers are softened.