Preheat the oven to 350°F (175°C).

In a large bowl, cream the softened butter, brown sugar, and granulated sugar until smooth and fluffy.

Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Blend in the vanilla extract.

In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon if using. Gradually fold the dry ingredients into the wet mixture for a uniform dough.

Stir in the oats and raisins, making sure they’re evenly mixed.

Drop spoonfuls of dough onto ungreased baking sheets, spacing them apart to allow for spreading.

Bake for 10 to 12 minutes, or until the edges turn golden brown.

Let the cookies cool on the baking sheets for a few minutes before transferring them to wire racks to cool completely.