Mix flour, oatmeal, baking powder, salt, and brown sugar in a large bowl. Whisk in the milk and vanilla until the batter is combined.
Heat a large non-stick griddle or skillet over medium heat and grease with butter as needed.
Pour 1/3 cup of batter into circles.
Flip once bubbles appear on top and the bottom is golden brown. Cook until firm and golden brown on both sides. (Keep pancakes warm in a 200°F oven until all are done if desired.)
In the meantime, in a non-stick pan over medium heat, brown the chicken sausage on both sides.
Use remaining butter and maple syrup (if desired) on the pancakes, garnish with granola, and serve with chicken sausage and oranges.