Step 1: Preheat your oven to 350°F (175°C).
Step 2: In a large pot, prepare the yellow rice according to the package instructions. Once cooked, set aside.
Step 3: In a large mixing bowl, combine the cooked yellow rice, Mexicorn, chopped chicken, black beans, diced tomatoes and green chiles, cream of chicken soup, southwestern seasoning, and half of the shredded cheddar cheese. Stir until everything is evenly mixed.
Step 4: Add salt and pepper to taste, making sure to taste the mixture as you go to achieve the desired flavor.
Step 5: Pour the mixture into a greased 9x13-inch casserole dish, spreading it out evenly.
Step 6: Sprinkle the remaining shredded cheddar cheese over the top of the casserole.
Step 7: Place the casserole in the preheated oven and bake for 30-35 minutes, or until the cheese is bubbly and golden.
Step 8: Remove from the oven and let it cool for a few minutes before serving.