Cook the ground beef and onion together in a large skillet over
medium heat until the beef is completely browned; stir the barbeque
sauce and Cheddar cheese into the ground beef. Pour the mixture
into a 9×13-inch dish
Whisk the baking mix, eggs, and milk together in a bowl; pour over
the beef mixture
Bake in the preheated oven until the crust is golden brown and
cooked throughout, about 25 minutes