Preheat Ove: Set to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
Cook Meat & Onion: In a skillet, brown the ground beef with diced onion until fully cooked. Drain excess grease.
Mix Filling: Stir in frozen vegetables, cream of mushroom soup, milk, garlic powder, salt, and pepper. Simmer for 5 minutes.
Assemble Hotdish: Pour the filling mixture into the prepared baking dish. Spread evenly.
Cheese Layer: Sprinkle shredded cheddar cheese over the filling (optional for extra richness).
Top with Tater Tots: Arrange tater tots in a single, even layer across the top.
Bake: Place in oven uncovered for 40–45 minutes, or until tots are golden and crispy and filling is bubbling.
Cool & Serve: Let rest for 5 minutes before serving.