Preheat the oven to 375 degrees. Prepare baking dish by spraying it with non-stick cooking spray, and set aside.
In a medium mixing bowl, mix cornbread according to package instructions using eggs and milk, and set aside.
In a large skillet over medium heat, brown ground beef with the diced onion until no longer pink. Drain well. Add the Rotel, beans, corn, and taco seasoning.
Spoon meat mixture into the prepared casserole dish. Spoon cornbread overtop and smooth evenly.
Bake uncovered in preheated oven for 40 minutes or until a toothpick inserted into the middle of the casserole comes out clean. Cover loosely with foil and allow to sit 10 minutes before serving.
Notes
Garnish with a dollop of sour cream, fresh cilantro, sliced green onions, or pico de gallo.