Preheat your oven to 400°F (200°C).
In a large skillet over medium heat, brown the ground beef (or sausage) with the diced onion and bell pepper until fully cooked. Drain any excess fat.
Stir in the pizza sauce, Italian seasoning, and garlic powder, mixing well to combine. Let the mixture simmer for about 5 minutes.
In a large mixing bowl, combine the cooked meat mixture with half of the shredded mozzarella cheese and half of the sliced pepperoni.
Spread the meat and cheese mixture evenly in the bottom of the greased 9x13 inch baking dish.
Top the meat mixture with the frozen tater tots, arranging them in a single layer.
Sprinkle the remaining mozzarella cheese and pepperoni over the top of the tater tots.
Bake in the preheated oven for 30 minutes, or until the tater tots are golden brown and crispy.
Remove from the oven, let it cool for a few minutes, then serve hot.