In a large mixing bowl, add oats, protein powder, pumpkin pie spice, cinnamon, and salt. Stir to combine evenly so spices don't clump later.
In a smaller bowl, whisk pumpkin puree, nut butter, maple syrup, and vanilla until smooth and glossy.
Pour the wet mixture into the dry ingredients. Stir with a sturdy spatula until a dough forms. If it's crumbly, add milk 1 teaspoon at a time. If it's sticky, add a tablespoon of oats or protein powder.
Fold in chocolate chips or nuts if using. Keep them small so the bites hold together.
Scoop about 1 heaping tablespoon of dough (a small cookie scoop helps) and roll into 1-inch balls. You should get 14–18 bites, depending on size.
Roll bites in cinnamon, crushed pecans, or coconut for extra texture. Fancy? Yes. Necessary? No. Delicious? Absolutely.
Place bites on a parchment-lined plate and refrigerate for 30 minutes. They firm up and taste better cold.
Enjoy straight from the fridge or let sit 5 minutes for a softer bite.