Preheat oven to 350°F and arrange oven rack to the middle position. Line baking trays with parchment.
In a medium bowl whisk together flour, baking soda and salt. Set aside.
Beat together both sugars and melted butter until light and creamy. Add whole eggs one at a time, and then the egg yolk, incorporating after each addition. Scrape bowl and mix in vanilla.
Add flour mixture all at once and mix until incorporated. Add oatmeal and mix to combine. Scrap bowl and stir in chocolate chips.
Using a 1-ounce cookie scoop, scoop the batter onto prepared trays spacing evenly at least 2 inches apart. Flatten cookies with the palm of your hand or the bottom of a cup.
Bake one tray at a time for 10-11 minutes (do not overbake). Remove from oven and allow to cool for 5 minutes on the tray before moving to a cooling rack.
Repeat with the remaining cookie dough.