Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine ground beef, breadcrumbs, egg, onion, garlic powder, salt, and black pepper.
Shape the mixture into a loaf and place it in a greased baking dish.
Bake the meatloaf in the oven for about 45 minutes.
While the meatloaf is baking, prepare your mashed potatoes according to your recipe or package instructions.
Remove the meatloaf from the oven and spread the mashed potatoes evenly over the top.
Top the mashed potatoes with shredded cheddar cheese and crumbled bacon.
Return the baking dish to the oven and bake for an additional 15–20 minutes until the cheese is bubbly.
Let the casserole cool for a few minutes before garnishing with green onions.
Serve warm and enjoy!