Preheat your oven to 350°F and lightly grease a donut pan with the coconut oil.
In a medium mixing bowl, whisk together the oat flour, chocolate protein powder, cacao powder, baking powder, and sea salt until well combined.
In a separate bowl, whisk the 0.5 cup Greek yogurt, egg whites, 1 tablespoon maple syrup, and vanilla extract until the mixture is smooth.
Gently fold the wet ingredients into the dry ingredients using a spatula until just combined, ensuring you do not overmix the batter.
Spoon or pipe the batter into the prepared donut pan cavities, filling each about three-quarters of the way to the top.
Bake for 12 to 15 minutes, or until the donuts are springy to the touch and a toothpick comes out clean.
Allow the donuts to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
Prepare the glaze by whisking together the remaining tablespoon of Greek yogurt, teaspoon of cacao powder, and teaspoon of maple syrup in a small bowl.
Once the donuts are cool, dip the top of each donut into the chocolate glaze and enjoy.