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 light and fluffy. This should take about 2-3 minutes using an electric mixer.

Beat in the eggs one at a time, ensuring each is fully incorporated. Add the vanilla extract and mix until combined.

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

Using a spatula, gently fold in the rolled oats and raisins or chocolate chips (if using) until evenly distributed.

Drop rounded tablespoons 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. Enjoy warm or store in an airtight container for up to a week.