Preheat oven to 350 degrees and line a muffin tin with paper liners.
In a large bowl whisk together the flour, oats, baking powder, baking soda, salt, ground flaxseed meal, and cinnamon.
In another large bowl whisk together the applesauce, brown sugar, eggs, banana, peanut butter, and milk.
Next add the dry ingredients to the wet and stir together until just combined. (it might be a little lumpy, that is totally ok)
Fill prepared muffin cups with batter and bake for 18-20 minutes until toothpick comes out clean.
Allow muffins to cool for 5-10 minutes then let them cool completely on a wire cooling rack.