Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.
In a large bowl, beat the softened butter, brown sugar and granulated sugar together until light and fluffy, about 2 minutes.
Beat in the eggs one at a time, then add the vanilla and mix until smooth.
In a medium bowl, whisk together the flour, baking soda, cinnamon and salt.
Add the dry mixture to the butter mixture and stir just until no dry flour remains.
Fold in the oats and chocolate chips until evenly distributed.
Cover the bowl and refrigerate the dough for 30 minutes.
Scoop the dough into balls of about 2 tablespoons each and place them 2 inches apart on the prepared sheets.
Gently press each ball down with your palm so it’s about ¾ inch thick.
Bake one sheet at a time for 10 to 11 minutes, until the edges are golden and the centers still look slightly soft.
Sprinkle with flaky salt if you like. Let the cookies rest on the sheet for 5 minutes, then move them to a wire rack.
