Preheat your oven to 400°F (200°C).
In a skillet, cook the ground beef and chopped onion over medium heat until the beef is browned and fully cooked. Drain any excess fat.
Season with salt and pepper, then spread the beef mixture into a greased 9-inch pie dish.
Sprinkle shredded cheddar cheese evenly over the beef.
In a medium bowl, whisk together the Bisquick mix, milk, and eggs until smooth.
Pour the batter over the beef and cheese.
Bake for 25 minutes or until a knife inserted into the center comes out clean.
Let it cool for a few minutes before slicing and serving.