Bring 3 cups chicken broth to a boil in a saucepan, then add the quinoa. Reduce heat to a simmer, cover, and let cook until the liquid has been mostly absorbed and the quinoa is tender, about 15 minutes, depending on the brand of quinoa you purchase. Keeping the pan covered, remove from heat and let stand 10 minutes. Uncover, lightly fluff with a fork, and set aside.

Preheat oven to 350 degrees. Spray an 9×13-inch baking dish with nonstick spray.

Heat 1 Tbsp. olive oil in a large, deep skillet over medium heat. Add onion, diced bell pepper, corn, and garlic. Add the salt and pepper and taco seasoning. Cook for about 5 minutes. Add in the chicken and beans; mix well, and remove to a large bowl.

In the same pan, melt the butter; sprinkle the flour over the top and briskly whisk (it will be gooey). Cook for 30 seconds, and then pour in the remaining 1 cup chicken broth and the milk. Salt and pepper to taste.

Whisk constantly, breaking up any lumps; add 2 cups of cheese and mix well.  Add the oregano. Increase the heat to bring the mixture to a simmer, then reduce the heat and let gently bubble until the sauce has thickened slightly, about 5 minutes, stirring often.

Remove skillet from heat, and pour into the quinoa and chicken mixture. Pour into the prepared baking dish; sprinkle the top with the remaining 2 cups of cheese. Sprinkle with dried cilantro.

Bake for 20-25 minutes, until the top is golden and bubbly. Let cool 10 minutes, then serve with your favorite toppings, such as sour cream, salsa, green onions, or fresh tomatoes.