Preheat oven to 350 degrees. In a large bowl combine eggs, milk, salt and pepper. Whisk together and set aside. Alternatively, if using tofu combine tofu, milk, salt and pepper in a blender and process until smooth.
Spray a large oven safe pan with olive oil. Add onion and cook for 10 to 12 minutes, or until tender. Add sausage and cook until heated through. Remove from heat.
Stir onion mixture with cooked quinoa and spinach. Pour egg or tofu mixture over and then top with cheeses.