Cook rice according to package directions. While rice is cooking saute onion in butter and olive oil until transparent and soft. Add garlic and cook and stir 1 minute. Add seasonings and stir in beans and corn. Add enchilada sauce and rice.*
Transfer rice mixture to a large greased casserole dish and stir in Mexican cheese. Top with cheddar. Refrigerate, covered, up to 48 hours before baking. Bake at 350 degrees 30-40 minutes until hot and bubbling.
Notes
*If you want to serve this right away, add cheeses to skillet, cover skillet and let cook for 2-3 minutes or until cheese has melted.Note: this is not spicy at all so kick it up with chilies, hot sauce or jalapenos if desired.