Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats to prevent sticking.

In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until the mixture is light and fluffy.

Beat in the eggs one at a time, followed by the vanilla extract. Mix until everything is well combined and smooth.

In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon. Gradually add this dry mixture to the wet ingredients, mixing just until combined.

Stir in the rolled oats and, if desired, raisins or chocolate chips.

Using a cookie scoop or tablespoon, drop rounded portions of dough onto the prepared baking sheets, spacing them about 2 inches apart. Bake in the preheated oven for 10–12 minutes, or until the edges are golden brown and the centers look slightly underbaked.

Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.