In a large mixing bowl, whisk together 1/2 cup pumpkin puree, 1/2 cup plain Greek yogurt, 1/2 cup milk, 1/4 cup light olive oil, 1/4 cup maple syrup, 1 teaspoon vanilla extract, and 3 eggs until completely smooth and well combined.
Add 1 cup oat flour, 1/2 cup vanilla protein powder, 1 tablespoon baking powder, 1 teaspoon cinnamon, 1 teaspoon pumpkin pie spice, and 1/4 teaspoon salt and whisk until smooth. Be careful not to overmix.
Pour the recommended amount of batter for your waffle iron and cook according to your machine's settings until golden brown and crispy.
Allow waffles to cool slightly before serving to let them firm up. Serve immediately with your favorite toppings, or cool completely before storing in the refrigerator for up to 5 days or freezer for up to 3 months.