1. Preheat a large skillet over medium-to-high heat, add the beef or bison and brown until about 80% cooked through. Add about 1-2 Tbsp of taco seasoning for the last few minutes. Remove from heat temporarily.
2. In the same skillet add the bell pepper, onion, celery, and corn and fry until the vegetables just start to soften.
3. Add the remaining ingredients, a bit more taco seasoning, and the beef/bison back into the skillet, but don’t add the spinach, green onions, or feta cheese. Mix well, cover & let simmer until the quinoa is cooked ~15 minutes.
4. Stir in the spinach and let it cook for just a few minutes until cooked down.
5. Remove from heat and top with feta, onions, and optional toppings like pickled red onions, pickled jalapenos, salsa, guacamole, etc.