In the bowl of a stand mixer fitted with a paddle attachment or a large mixing bowl with a handheld attachment, add the butter. Beat on medium-low speed for 2 minutes. Add the sugars and beat on medium-low speed for 1 minute.
Add the eggs one at a time, mixing well after each addition. Add the vanilla and mix to combine.
In a separate mixing bowl whisk together the oats, flour, baking soda, salt, and cinnamon. With mixing speed on low, gradually add the dry ingredients. Mix just until a few flour streaks remain.
Add in chocolate chips and mix until combined.
Cover dough and place in the refrigerator to chill for 30 minutes. This is an important step, so DO NOT SKIP.
Preheat oven to 350 degrees. Line a baking sheet with parchment paper or a silicone baking mat.
Using a standard size cookie scoop, portion the dough into balls. Place 12 on a sheet.
Place in the oven and bake for 11-13 minutes or until the edges begin to brown and the middle is set. Remove from the oven and allow to cool on the sheet for 3 minutes before transferring to a wire rack to cool completely.
Repeat with remaining dough.
Note: you can swap out the chocolate chips for raisins.