Preheat oven to 350ºF.
Line baking sheets with parchment paper or silicon baking pad.
In a medium bowl with a wooden spoon, stir together the oats, sugar, baking powder, and salt.
In a separate bowl stir the vanilla into the beaten egg until well incorporated.
Continuously stirring the egg mixture, slo-o-owly pour the melted butter into the egg. Add the butter slowly so it incorporates and doesn't have a chance to cook to egg.
Add this egg mixture to the oats and mix thoroughly. You should have a sticky mixture that is still loose; don't worry, when the cookies bake, the egg will bind it all together.
If using, add the chocolate chips and stir until evenly distributed.
Use a Tablespoon or cookie scoop to drop onto prepared cookie sheets. Before dropping onto the cookie sheet be sure to press the mixture a bit to compact it. Then gently press on the cookie to flatten a little before baking. These won't spread out.
Bake for 9-12 minutes until edges are golden brown. Cooking time will determine the crispiness or chewiness of these cookies...longer cooking = crispier, just watch to ensure they don't burn.
Remove cookies from baking sheet to cooling rack while still warm.