In a large skillet over medium-high heat, cook ground beef with diced onion for 6-8 minutes until beef is browned. Add minced garlic and cook 1 more minute until fragrant.
Drain off any excess fat from the skillet.
Stir in condensed cream of mushroom soup, undrained diced tomatoes, water, Worcestershire sauce, oregano, salt, and pepper. Bring mixture to a simmer.
Stir in uncooked elbow macaroni until well combined.
Transfer mixture to a 9×13 inch baking dish and spread into an even layer.
Cover dish with foil and bake for 30 minutes.
Remove foil, sprinkle shredded cheddar cheese evenly over top, and bake uncovered for 10-15 minutes until cheese is melted and bubbly.
Let casserole rest for 5 minutes before serving.
Notes
Use 80/20 ground beef for best moisture and flavor. Ground turkey or chicken works too with 1-2 tablespoons olive oil added.
Any small pasta shape works well including shells or rotini. If sauce seems thick before baking, add extra 1/4 cup water.
Can be assembled 24 hours ahead and refrigerated. Add 5-10 minutes to baking time if starting cold.