Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.
In a large bowl, cream together softened butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in vanilla.
In a separate bowl, whisk together flour, baking soda, cinnamon, nutmeg, and salt.
Gradually stir the dry ingredients into the wet mixture.
Fold in oats and raisins until evenly combined.
Drop rounded tablespoons of dough onto the prepared baking sheet, spacing 2 inches apart.
Bake for 8–10 minutes or until the edges are lightly golden and centers are still soft.
Let cookies cool on the sheet for 2 minutes before transferring to wire racks to cool completely.