Preheat the oven to 400°F and lightly coat a 9×13-inch baking dish with nonstick cooking spray.
Brown the ground beef in a large skillet over medium-high heat, breaking it apart as it cooks. Drain any excess grease, then add the taco seasoning and prepare the beef according to the seasoning packet directions.
Add the dry orzo to the prepared baking dish. Add the taco-seasoned ground beef, Rotel, corn, diced onion and garlic.Pour in the beef broth, then season everything with salt, pepper, cumin, garlic powder and chili powder.
Stir everything together well, making sure the orzo is evenly distributed and mostly submerged in the liquid. Cover the baking dish tightly with aluminum foil and bake for 40 minutes. Carefully remove the casserole from the oven and stir the orzo. Turn the oven off.
Sprinkle the shredded cheddar and Monterey Jack evenly over the top. Cover the baking dish again and return it to the warm oven for about 5 minutes, or until the cheese is completely melted. Remove the casserole from the oven, let it rest for about 5 minutes, then serve warm.