In a small microwave-safe bowl add the raisins along with ¼ c. of water. Cover with plastic wrap and microwave for 30 seconds then allow to sit covered until needed.
In the bowl of a stand mixer, beat together butter, sugars and vanilla extract for 2-3 minutes. Add the egg then mix until combined.
In a medium size mixing bowl, combine flour, oats, baking soda, cinnamon, nutmeg, and salt. Whisk to combine. With mixing speed on low, gradually add dry ingredients, mixing until no flour pockets remain. Remove bowl from stand and fold in raisins (drain any excess moisture from the bowl before adding them). Cover the bowl and place in the dough in the refrigerator to chill for 1 hour before baking.
Preheat oven to 350 degrees. Line baking sheets with parchment paper or baking mats, set aside.
Using a standard size cookie scoop, place balls of chilled dough onto the prepared cookie sheets. Place in the oven and bake for 10-12 minutes, or until the edges of the cookies begin to turn golden brown in color. The centers should look slightly underbaked, they will firm up once cooled. Remove from oven and allow cookies to cool on sheets for 3-4 minutes before transferring to a wire rack to cool completely.
Notes
-You could easily swap out the raisins for chocolate chips (just up the vanilla extract by ½ tsp. and omit the cinnamon and nutmeg). Sometimes I'll add toffee chunks too!