Preheat your oven to 350°F and line a baking sheet with parchment paper or a silicone mat.
In a medium mixing bowl, whisk together the egg, nonfat Greek yogurt, maple syrup, and vanilla extract until the mixture is smooth and well combined.
Add the rolled oats, vanilla protein powder, ground cinnamon, baking powder, and sea salt to the wet ingredients.
Stir the mixture with a spatula until a thick, uniform dough forms and all the powder is fully incorporated.
Divide the dough into 4 equal portions and roll them into balls, then place them on the prepared baking sheet.
Gently press down on each ball with the back of a spoon to flatten them into cookie shapes, as they will not spread much during baking.
Bake for 10 to 12 minutes until the edges are lightly golden and the cookies feel firm to the touch.
Remove from the oven and allow the cookies to cool on the baking sheet for at least 5 minutes to set their chewy texture before serving.