Preheat the oven to 350 F. Lightly grease 12 muffin cups with non-stick cooking spray.
In a large mixing bowl, whisk together the oats, brown sugar, baking powder, cinnamon and salt.
Add the milk, eggs, applesauce, vanilla to the dry ingredients and whisk together. The batter will be "liquidy" compared to other batters you have made.
Pour the batter into the prepared muffin cups. Bake in the preheated oven for 25 to 30 minutes, or until cups are cooked through. Let cool completely before serving.
FREEZING INSTRUCTIONS: Let the muffins cool completely before adding to resealable baggie or container. Freeze in fridge freezer for 6 months or deep freezer for 12 months. To reheat, remove from container and let return to room temperature on counter, or run on defrost in the microwave for a minute.