Cook and stir ground beef in a large skillet over medium heat until browned and crumbly, about 10 minutes; season with salt, black pepper, garlic powder, and onion powder.
Drain excess grease. Stir cream of mushroom soup and green beans into ground beef and bring to a simmer.
Spread ground beef mixture into a 9x13-inch casserole dish.
Spread mashed potatoes evenly over ground beef mixture.
Sprinkle Cheddar cheese over the top.
Bake in the preheated oven until heated through, about 20 minutes.