Preheat your oven to 350°F (180°C) and line a few baking sheets with parchment so they’re ready to go.

In a bowl, whisk together the flour, baking soda, cinnamon, salt, and nutmeg. Set aside.

In the bowl of a stand mixer, beat the butter until it’s smooth and creamy. Add both sugars and continue mixing until the texture is fluffy and light. Blend in the egg and vanilla until everything is silky and combined.

Lower the speed and add in the dry ingredients just until they come together. Mix in the oats, followed by the raisins, finishing with a spatula so every bit of the dough is even.

Scoop the dough into balls, about two tablespoons each, and arrange them on your baking sheets, spacing them well.

Bake one sheet at a time for 12 to 14 minutes, rotating halfway through. The edges should turn golden while the centers still look slightly soft—that’s what keeps them chewy. Give the pan a gentle tap on the oven rack before pulling it out.

Let the cookies cool on the pan over a wire rack until set.