Heat oven to 400°F
In 10-inch cast iron skillet, cook beef and onion over medium heat 4 to 5 minutes, stirring occasionally.
While the hamburger is cooking, heat frozen veggies in a microwave for about 2 minutes and then drain.
Stir in sale, garlic powder, and drained vegetables. Cook 4-5 minutes more.
While that is finishing cooking, whisk the baking mix, milk, and eggs together in a bowl.
When the hamburger is done, turn off the heat and top with the cheese.
Pour the baking mix evenly over the top of your hamburger and place in the oven for about 30 minutes, or until done.
Let stand 10 minutes before serving.