Preheat your oven to 350°F (175°C).
In a bowl, mix together the oat flour, pumpkin purée, and peanut butter (and optional egg) until a dough forms.
If using cinnamon, sprinkle it in and mix again.
Roll the dough out between two pieces of parchment paper to about ¼ inch thick or use oat flour to keep dough from sticking to rolling pin.
Use your favorite cookie cutters to cut out shapes.
Place the shapes on a parchment-lined or cooking oil sprayed baking sheet.
Bake for 18–22 minutes, or until firm and slightly golden.
Let cool completely before giving them to your pup.