Preheat your oven to 375°F (190°C).
In a large skillet over medium heat, cook the ground beef and diced onion until the beef is browned and the onion is softened, about 5-7 minutes. Drain any excess grease.
Stir in the condensed cream of mushroom soup, condensed cream of chicken soup, and frozen mixed vegetables. Season with salt and pepper to taste. Cook for an additional 2-3 minutes, until heated through.
Transfer the beef mixture to a 9x13 inch baking dish, spreading it evenly.
Sprinkle the shredded cheddar cheese over the beef mixture.
Arrange the frozen tater tots in a single layer over the cheese.
Bake in the preheated oven for 40-45 minutes, or until the tater tots are golden brown and crispy.
Remove from the oven and let it cool for a few minutes before serving.
Garnish with chopped parsley, if desired, and serve hot.