In a large skillet, heat the 3 tablespoons of olive oil over medium heat. Add the diced onion and red bell pepper. Sauté for about 5-7 minutes, or until the onion becomes translucent and soft.
While the vegetables are cooking, rinse the quinoa under cold water. In a medium saucepan, combine the quinoa and 1 ½ cups of water. Bring to a boil, then reduce the heat to low, cover, and simmer for about 15 minutes, or until all the water is absorbed. Fluff with a fork and set aside.
Once the vegetables are ready, add the shredded chicken, cooked quinoa, black beans, corn, red enchilada sauce, cumin, smoked paprika, black pepper, and salt to the skillet. Stir everything together until well combined and heated through.
Sprinkle the 2 cups of shredded Mexican cheese blend over the top of the mixture. Cover the skillet and let it cook for about 5 minutes, allowing the cheese to melt beautifully.
Once the cheese is melted, remove the skillet from heat. Serve the Cheesy Chicken Enchilada Quinoa warm, garnished with the reserved diced red bell pepper, diced avocado, and minced cilantro if desired.