Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.
In a blender or food processor, grind the oats into a fine flour.
In a large bowl, combine the oat flour, protein powder, and baking powder.
In another bowl, whisk together the Greek yogurt, eggs, honey, vanilla extract, and milk.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Divide the batter evenly into the prepared muffin cups.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the pan for a few minutes before transferring to a wire rack to cool completely.