Preheat your oven to 350°F and line two baking sheets with parchment paper.
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 3 minutes.
Beat in the eggs one at a time, then mix in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, cinnamon, nutmeg, and salt.
Gradually add the dry ingredients to the butter mixture, stirring until just combined.
Fold in the oats and raisins until evenly distributed throughout the dough.
Drop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake for 10-12 minutes, until the edges are golden brown but the centers still look slightly underdone.
Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.