Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

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.

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

Fold in the old-fashioned oats and, if desired, the raisins or chocolate chips.

Drop rounded tablespoons of dough onto the prepared baking sheets, leaving enough space between each cookie.

Bake for 10-12 minutes or until the edges are golden brown. The centers will still be soft.

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