Preheat your oven to 400ºF. Spray a 9x13 baking dish with baking spray and set aside.
Heat a large skillet over medium-high heat. Add the ground sausage, chopped pepper, and chopped onion to the hot skillet. Cook for about 10 minutes, chopping the meat as it cooks so that it is small crumbles. The meat should no longer be pink, and the peppers and onions should be soft.
1 ½ pounds ground breakfast sausage, 1 red bell pepper, seeds removed, chopped, 1 onion, chopped
Remove the skillet from the heat and stir in the hash brown potatoes and 1 ½ cups of the cheese.
2 cups shredded cheddar cheese, 3 cups frozen hash brown potatoes
Scoop the sausage mix into the prepared baking dish and spread it into an even layer.
In a seperate mixing bowl, whisk together the Bisquick, eggs, maple syrup, milk, salt, and pepper.
1 cup Bisquick baking mix, 4 eggs, 2 cups whole milk, 2 Tablespoons maple syrup, 1 teaspoon salt, ½ teaspoon ground black pepper
Pour the Bisquick mix into the casseorle dish.
Bake the casserole, uncovered, for 40 minutes. The casserole should be golden brown, and a knife inserted into the center of the casserole should come out clean.
Sprinkle the remaining ½ cup of cheese over the hot casserole and return it to the oven to bake for 3-4 more minutes just to melt the cheese.
Serve while hot!