01 - 
                Preheat the oven to 400°F. Grease a 9-inch glass pie plate with vegetable oil.
              
              
              
                02 - 
                Heat oil in a large skillet over medium heat and cook the chopped onion until soft, about 3 minutes.
              
              
              
                03 - 
                Add ground beef to the skillet, breaking apart with a spatula. Cook until browned, about 10 minutes. Drain excess fat and season with salt, black pepper, and garlic powder if desired.
              
              
              
                04 - 
                Spread the cooked beef mixture evenly in the prepared pie plate. Sprinkle grated Cheddar cheese over the beef layer.
              
              
              
                05 - 
                In a small bowl, whisk together Bisquick mix (or all-purpose flour), milk, and eggs. Pour the mixture over the beef and cheese layers in the pie plate.
              
              
              
                06 - 
                Bake for 20 to 25 minutes, or until a knife inserted in the center comes out clean.
              
              
              
                07 - 
                Serve warm and enjoy this comforting slice of cheeseburger pie.