Preheat your oven to 350°F (175°C).
In a large skillet, brown the ground beef over medium heat. Add chopped onion and minced garlic, and sauté until the onion is translucent. Drain excess fat.
In a large mixing bowl, combine the browned beef mixture with diced potatoes, green beans, corn, cream of mushroom soup, salt, pepper, and oregano. Mix until well combined.
Transfer the mixture into a greased 9x13-inch baking dish. Spread it evenly.
Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil, sprinkle shredded cheddar cheese on top, and return to the oven to bake uncovered for an additional 15 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for a few minutes before serving.