Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the softened unsalted butter, light brown sugar, and granulated sugar. Beat on medium speed until light and fluffy, about 2-3 minutes.
Add the egg and vanilla extract to the mixture and beat until well combined.
In a separate bowl, whisk together the oats, flour, cinnamon, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Gently fold in the chocolate chips and optional raisins or nuts.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto a prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, or until the edges are golden and the centers are still soft.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.
