In a pot over medium heat bring water/stock to a boil.
Add oats, red onion, salt and garlic powder, stir to combine and and lower the heat. Cook for 8-10 minutes, stirring often, until the oatmeal is creamy and tender. Stir in maple syrup, if using.
Meanwhile heat a skillet over medium-high heat. When hot add oil and ground breakfast sausage. Cook until the sausage is brown. Remove sausage to a plate lined with paper towel (or a clean kitchen towel) and let excess fat drain.
Divide oatmeal into 4 bowls and top with sausage, green onions, cheese and eggs, if desired. If cooking for meal prep do not add cheese until after it has be re-heated.
Can omit cheese and add in 1 tablespoons of nutritional yeast into the oatmeal if looking for a "cheesy" taste.