Preheat the oven to 350 degrees F. and grease a donut pan with cooking spray (Baker's Joy recommended for easy release).
Grind the oats in a food processor until it reaches the consistency of flour. *Measure the oats before grinding. Blend cottage cheese until smooth (you'll use 1/4 cup of blended cottage cheese for the batter).
Add all ingredients to a large bowl and mix well with a wooden spoon until combined and smooth.
Pour batter evenly into the six molds of the donut pan. If you have smaller donut pans it may make 7-8 donuts.
Bake 12 minutes until cooked through and a toothpick comes out clean (do not overbake).
Whisk the frosting ingredients together, stirring the milk and protein powder together first until smooth, then stirring in the cooled melted butter until a frosting consistency is achieved. If making the classic glaze, stir all ingredients together in a small bowl.
After donuts have cooled completely, brush, dunk, or drizzle with your glaze of choice.
Top with 1 tbsp of your favorite cereal, mini chocolate chips, or another tasty topping, right before serving.
Enjoy immediately. These donuts are best enjoyed freshly baked.