Preheat oven to 400°F (200°C).

In a skillet over medium heat, cook ground beef and chopped onion until browned. Drain excess fat.

Spread the beef mixture evenly into a greased 9-inch pie plate.

Sprinkle shredded cheddar cheese over the beef.

In a separate bowl, whisk together Bisquick, milk, eggs, salt, and pepper until smooth.

Pour the batter evenly over the beef and cheese.

Bake for 25–30 minutes or until the top is golden and a knife inserted in the center comes out clean.

Let cool for 5 minutes before slicing and serving.