Preheat the oven to 400°F. Bring chicken stock to boil over medium heat. Add quinoa, reduce heat to low and cook until tender, about 15-20 minutes. Set aside.
Prepare the bell peppers. Cut each pepper in half lengthwise and remove seeds. Drizzle with 2 tsp olive oil, and bake for 10 minutes. Remove from oven and set aside.
Heat a frying pan on the stove over medium heat. Add remaining 1 tsp olive oil and diced onion and cook until soft, about 5 minutes. Add ground beef and cook until no longer pink, breaking apart large pieces in the pan with a wooden spoon. Drain any excess fat out of the pan before continuing. Add chili powder, garlic, onion powder, oregano, paprika, cumin, salt, and pepper and cook for 30 seconds. Add in crushed tomatoes and stir in cooked quinoa. Season with additional salt and pepper if desired.
Fill each pepper half with ground beef filling and top with a sprinkle of cheese. Bake for 20 minutes until peppers are soft and cheese is melted.
Notes
You can substitute the seasonings listed with a low sodium taco seasoning packet or homemade taco seasoning! Just use 4 Tbsp seasoning instead!