Preheat oven to 350 degrees F (175 degrees C). Grease a 9-inch square baking dish.
Mix hash brown potatoes, vegetable oil, and black pepper in a bowl; press into the bottom of the prepared baking dish.
Heat a large skillet over medium-high heat. Cook and stir beef, garlic powder, and onion powder in the hot skillet until beef is browned and crumbly, 5 to 7 minutes; drain and discard grease.
Mix water and gravy mix into the cooked beef; bring to a boil. Reduce heat, cover skillet, and simmer until water evaporates, about 5 minutes. Fold in 1/2 cup Cheddar cheese. Spoon beef mixture onto the potato crust.
Bake in the preheated oven for 15 minutes. Sprinkle remaining 1/2 cup Cheddar cheese and bake until cheese is lightly browned, about 5 more minutes.