Step 01 Preheat oven to 350°F (175°C) and lightly grease a 9×13-inch baking dish. Step 02 Cook ground beef in a large skillet over medium heat, breaking up the meat until completely browned. Drain any excess fat. Step 03 Add taco seasoning, diced tomatoes with green chilies, condensed cheddar cheese soup, and milk to the browned beef. Stir thoroughly and simmer for 5 minutes until well combined. Step 04 Evenly spread half of the crushed Doritos across the bottom of the prepared baking dish. Step 05 Pour the prepared beef mixture over the first layer of Doritos, smoothing it into an even layer. Step 06 Sprinkle the remaining crushed Doritos evenly over the beef layer. Top with shredded cheddar cheese. Step 07 Bake for 15–20 minutes until cheese is fully melted and casserole is bubbling around the edges.