Add oats, milk, diced apple, vanilla, cinnamon, nutmeg, allspice, and salt to a small saucepan. Bring to a gentle simmer over medium heat.
½ cup rolled oats, 1 cup milk, ½ medium apple, ½ tsp vanilla extract, ½ tsp cinnamon, 1 pinch nutmeg, 1 pinch allspice, 1 pinch salt