Add all the dry ingredients to a 16-ounce jar or meal prep container. Use a long-stem fork to thoroughly combine all the ingredients.
Mix in the milk. Look at the underside of the container for any pockets of dry ingredients, and incorporate those as well.
Refrigerate the oats for at least 4 hours, though overnight is best.
Optional: Refrigerate the oats while making the icing. Add all of the icing ingredients to an immersion or high-power blender. Blend, occasionally scraping down the sides, until the icing is completely smooth and creamy.
Optional: Smooth the icing over (slightly set) oats and place them back in the fridge to finish setting. If the oats are still too wet, refrigerate the icing separately for the morning.
When ready for breakfast, top the oats with a bit more cinnamon and some chopped pecans for crunch.
Notes
Be sure to use a protein powder you really enjoy the taste of, as most of the icing flavor comes from the protein.
Nutrition information is calculated with icing and toppings.