In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract until combined.

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

Preheat the oven to 350°F. Drop tablespoon-sized balls of dough onto the prepared baking sheet, spacing them about 2 inches apart. Bake for 10-12 minutes or until the edges are golden brown. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.

Once cooled, store the cookies in an airtight container at room temperature for up to a week. To maintain their chewy texture, add a slice of bread to the container, which will help keep them moist.