Preheat your oven to 350°F (175°C).
In a large skillet over medium heat, cook the ground beef until browned. Drain any excess fat.
Add chopped onion and bell pepper to the skillet and sauté until softened, about 5 minutes.
In a large mixing bowl, combine sliced potatoes, green beans, cream of mushroom soup, garlic powder, salt, black pepper, and paprika. Stir in the cooked beef mixture along with ½ cup of water until well combined.
Transfer the entire mixture into a greased 9x13-inch baking dish and spread it evenly.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and sprinkle the shredded cheddar cheese on top. Return it to the oven, uncovered, for an additional 20 minutes, or until the potatoes are tender and the cheese is melted and bubbly.
Allow the casserole to cool for a few minutes before serving.