Preheat oven to 350°F (175°C) and line a 12-cup muffin tin with paper liners or coat with non-stick cooking spray.
In a large mixing bowl, whisk together the pumpkin puree, Greek yogurt, maple syrup, eggs, and vanilla extract until the mixture is homogenous.
In a separate medium bowl, sift together the oat flour, protein powder, pumpkin pie spice, baking soda, baking powder, and salt.
Gradually incorporate the dry ingredients into the wet ingredient mixture using a spatula, folding gently until no dry streaks remain.
Distribute the batter evenly among the 12 muffin cups, filling each approximately three-quarters full.
Bake for 20 to 24 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove from the oven and allow muffins to cool in the tin for 5 minutes before transferring to a wire rack for complete cooling.