Preheat the oven to 350°F (175°C).
In a large mixing bowl, whisk together the eggs, milk, salt, black pepper, garlic powder, and paprika until well combined.
Add the frozen diced potatoes, diced onion, diced green bell pepper, and shredded cheddar cheese to the egg mixture. Stir gently to combine all ingredients evenly.
Lightly grease a 9×13 inch baking dish with melted butter.
Pour the mixture into the prepared baking dish and spread it out evenly.
Cover the dish tightly with aluminum foil.
Bake in the preheated oven for 40 minutes.
Remove the foil and continue baking for an additional 10 minutes, or until the casserole is set and the top is lightly golden.
Remove from oven and let cool for 5 minutes before serving.