Preheat your oven to 400°F (200°C).

In a large skillet over medium heat, cook the lean ground beef and sweet onion until browned, about 7–10 minutes. Drain excess grease.

Spread the beef and onion mixture evenly in a greased 9-inch pie pan.

Sprinkle shredded cheddar cheese over the beef and onion mixture.

In a separate bowl, whisk together milk, onion soup mix, Bisquick, and eggs until well combined.

Pour the egg mixture over the beef and cheese layers in the pie pan.

Bake in the preheated oven for 25 minutes, or until the top is set and lightly golden.

Allow the pie to cool for 5 minutes before slicing and serving warm.