Add oil to a large skillet and brown the sausage and onion over medium high heat. Lightly season with salt and pepper and let it cool.
In a large bowl add the Bisquick, shredded cheese, Parmesan, milk, mayonnaise, egg, salt, pepper, garlic powder and the cooked sausage and onions. Stir everything together until it’s evenly combined.
Spray a loaf pan with cooking spray and place the sausage bread mixture inside. Spread it evenly into the pan.
Place it into the center rack of the oven for 50 minutes. Let it cool in the loaf pan for about 10 minutes.
Remove the sausage bread from the loaf pan, slice and serve warm.