Preheat the oven to 350°F. Spray a 2-quart casserole dish with cooking spray; set aside.
Cook the rice according to package directions. Once done, remove from heat and let the rice stand, covered, for 10 minutes to firm up.
In a medium bowl, stir together the sour cream, green chiles, Monterey jack cheese, corn, cilantro, cumin, salt, and black pepper.
Gently fold the cooked rice into the sour cream mixture until combined. Transfer to the prepared casserole dish.
Top with cheddar cheese and bake in the preheated oven for 30 minutes, until bubbly and lightly browned.