Heat oven to 350°F; line two sheets with parchment.
Cream butter and both sugars in a large bowl until fluffy, about 3 minutes.
Beat in eggs one at a time, then vanilla.
Whisk flour, baking soda, cinnamon, nutmeg, and salt in a separate bowl.
Gradually stir dry ingredients into butter mixture until just combined.
Fold in oats and raisins evenly.
Drop rounded tablespoons onto sheets, about 2 inches apart.
Bake 10-12 minutes until edges are golden and centers look slightly underdone.
Cool on sheets 5 minutes, then completely on a rack.