Preheat oven to 350 degrees F.
Place quinoa and water in a small pot and cook according to quinoa's package instructions. Typically this is to bring the water to a boil, reduce to low, cover, and cook for 15-20 minutes, or until quinoa has sprouted.
While quinoa is cooking, heat olive oil over medium-high heat in a large skillet.
Add the onion and cook until translucent, about 5 minutes.
Add ground chicken, and continue cooking, breaking up the chicken into small pieces, until chicken is cooked through.
Add chili powder, cumin, garlic powder, and salt, and stir well to combine. Remove from heat.
To the chicken, add corn, black beans, cheese, and cooked quinoa.
Place bell peppers in a 9x13" baking dish, cut side up.
Fill each bell pepper up with filling. Depending on the size of your bell peppers, you may have some filling left. Bigger bell peppers will fit a LOT of filling!
Bake in preheated oven for 35-40 minutes, until cheese is melty and peppers are softened.
Top with diced avocado and chopped cilantro. Serve immediately.