Rinse the quinoa: Place quinoa in a fine-mesh strainer and rinse under cold water for 30 seconds to remove bitterness.
Load the crockpot: Add onion, bell peppers, garlic, black beans, kidney beans, corn, diced tomatoes, tomato sauce, rinsed quinoa, and 3 cups of vegetable broth.
Season it up: Sprinkle in chili powder, cumin, smoked paprika, oregano, cayenne (if using), salt, and black pepper. Stir well to combine.
Cook low and slow: Cover and cook on Low for 6–8 hours or High for 3–4 hours, until vegetables are tender and quinoa is cooked.
Adjust consistency: If it’s too thick, stir in more broth.
If it’s too thin, let it cook uncovered on High for 15–20 minutes.
Brighten the flavor: Stir in lime juice. Taste and add more salt, pepper, or chili powder as needed.
Serve and top: Ladle into bowls and add your favorite toppings like avocado, cilantro, cheese, or a dollop of yogurt.