Preheat your oven to 400°F (200°C).

In a 9x13 inch baking dish, combine the finely diced onion, chopped red bell pepper, uncooked parboiled long-grain brown rice, and fajita seasoning. Mix these ingredients well.

In a separate bowl, whisk together the reduced sodium chicken broth, mild green chiles, tomato paste, and olive oil until fully blended.

Pour the whisked liquid mixture over the rice and vegetable combination in the baking dish. Stir gently until all ingredients are evenly coated.

Fold in the shredded chicken, drained and rinsed black beans, and frozen corn kernels into the dish.

Cover the dish tightly with aluminum foil and place it in the preheated oven. Bake for 65–70 minutes, until most of the liquid is absorbed and the rice is tender.

Remove the foil and sprinkle shredded Monterey Jack cheese evenly over the top. Return it to the oven for an additional 5–10 minutes, or until the cheese is melted and golden brown.

Allow the casserole to cool for 5–10 minutes before serving.