Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large bowl, cream together the butter, brown sugar, and granulated sugar until light and fluffy (2–3 minutes).
Add in the eggs and vanilla extract, beating until combined.
In a separate bowl, whisk together flour, baking soda, cinnamon, and salt.
Gradually mix the dry ingredients into the wet, just until combined.
Fold in the oats and chocolate chips by hand until evenly distributed.
Optional: Chill dough for 30 minutes for thicker cookies.
Scoop dough onto prepared baking sheet, spacing about 2 inches apart.
Bake for 10–12 minutes, until edges are lightly golden and centers look just set.
Let cool on the baking sheet for 5 minutes before transferring to a wire rack.