Get Ready: Preheat your oven to 375°F (190°C). Line a large baking sheet with parchment paper or a silicone baking mat for easy cleanup.
Mix Dry: In a medium bowl, whisk together the flour, baking powder, salt, cinnamon, and nutmeg. Set this aside.
Cream Wet: In a separate large bowl, use an electric mixer to beat the softened butter with both the granulated sugar and brown sugar until the mixture is light and fluffy, about 2-3 minutes.
Add Eggs & Vanilla: Beat in the vanilla extract, then add the eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl as needed to ensure everything is combined.
Combine: Gradually add the dry flour mixture to the wet butter mixture, mixing on low speed until just combined and no streaks of flour remain.
Stir in Oats & Raisins: Fold in the rolled oats until evenly distributed. Then, gently stir in the raisins (or chocolate chips if you prefer!). The dough will be nice and thick.
Scoop & Bake: Scoop the dough into tablespoon-sized balls, placing them about 2 inches apart on your prepared baking sheet. Bake for 12 to 15 minutes, or until the edges are lightly golden brown.
Cool Down: Let the cookies cool on the baking sheet for a few minutes before carefully transferring them to a wire rack to cool completely. Store any leftover cookies in an airtight container to keep them fresh and chewy.