01 -
Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 -
In a large skillet over medium heat, cook ground beef with chopped onion, breaking up the meat with a spatula, until beef is browned and onions are soft. Drain off excess fat.
03 -
Season the beef mixture with salt and pepper, then stir in the frozen mixed vegetables until evenly combined.
04 -
Transfer the beef and vegetable mixture to the prepared baking dish, spreading it out evenly.
05 -
Evenly layer diced potatoes over the beef and vegetable mixture.
06 -
Spread cream of mushroom soup evenly across the surface of the potatoes.
07 -
Cover tightly with aluminum foil and bake for 50 to 60 minutes, or until potatoes are fork-tender.
08 -
Uncover the dish, sprinkle shredded cheddar cheese over the top, and return to the oven for 10 to 15 minutes, until cheese is melted and bubbly.
09 -
Allow the casserole to rest for 5 minutes before serving.