Preheat oven to 375 degrees. Prepare a large baking sheet with parchment paper or nonstick cooking spray.
Place ½ cup oats into a food processor or blender and pulse until the oats are ground into flour like consistency.
In a large bowl, whisk together oats, oat flour, baking soda, cinnamon, salt, and flax.
In a medium bowl, whisk together the bananas, egg, and vanilla. Combine the wet ingredients with the dry ingredients.
Fold in the chocolate chips and pecans.
Using a large scoop, divide the dough into 16 cookies. Press the tops flat, as these cookies remain in the same shape as they cook.
Bake for 10 minutes of until the middle is set. Allow to cool on the baking sheet for 10 minutes before transferring to a wire rack.