Preheat your oven to 375°F (190°C) and lightly grease a baking dish.
In a large bowl, combine ground beef, onion, garlic powder, onion powder, salt, pepper, egg, breadcrumbs, and milk. Mix until just combined.
Press the meat mixture into the bottom of the prepared baking dish and bake for 20 minutes.
Remove from the oven and spread the mashed potatoes over the meatloaf layer.
Sprinkle cheddar cheese evenly over the mashed potatoes.
Top with crumbled bacon and return to the oven for an additional 15 minutes or until cheese is melted and bubbly.
Garnish with chopped green onions before serving.