Spray a baking tray with a bit of vegetable oil, and set aside.
Whizz 90g oats or 130g oats (if you plan to cut them) in a food processor until they become flour-like, about 1 minute. Mix 90g of the oats them with the peanut butter, egg, and water until a dough is formed. If using biscuit cutters, use the remaining oat flour to roll out your dough and cut it with biscuit cutters. If you are making circular biscuits, simply shape your dough into little balls, and flatten with a fork (biscuits will not spread by themselves.)
Place biscuits onto your baking tray. For the egg wash, mit the additional egg with a bit of water and brush onto the biscuits. Bake in the preheated oven until firm, about 12 minutes.
Let cool, and stick on Rudolph noses with a bit more peanut butter. Store in an airtight container.