Preheat the oven to 375°F (190°C).
In a large skillet, brown the ground beef over medium heat.
Add the diced onion and bell pepper and sauté until softened.
Stir in the ketchup, Worcestershire sauce, garlic powder, salt, and black pepper.
Transfer the meat mixture to a greased 9x13-inch baking dish.
Sprinkle the shredded cheddar cheese evenly over the meat mixture.
Top with an even layer of frozen tater tots.
Bake in the preheated oven for 30-35 minutes, until the tater tots are golden brown.
Let the casserole cool for 5-10 minutes before serving.