Brown ground beef and onions in a skillet over medium heat until no pink remains and onions are tender, about 8 to 10 minutes. Drain any fat. Season beef mixture with seasoning salt and pepper.
Add beef mixture to the bottom of the prepared pie plate and top with shredded cheese.
In a large bowl whisk together Bisquick, milk, and eggs. Pour the mixture over the ground beef and cheese.
Bake for 23-27 minutes or until a knife inserted in the center comes out clean. Serve with your favorite burger toppings.
Notes
Serve with your favorite burger toppings such as:
ketchup, mustard, or thousand island dressing
shredded lettuce or tomato slices
pickles
bacon
Leftovers will keep in an airtight container in the refrigerator for up to 4 days.