Transform these simple ingredients into delicious oatmeal raisin cookies by following these step-by-step instructions:

1. Preheat the oven: Set your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. Mix dry ingredients: In a medium-sized bowl, whisk together the oats, flour, baking soda, salt, cinnamon, and nutmeg. Set aside.
3. Cream butter and sugars: In a large mixing bowl, use an electric mixer to cream the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
4. Add eggs and vanilla: Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract.
5. Combine dry and wet ingredients: Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined.
6. Fold in raisins: Gently fold in the raisins (and nuts if using) using a spatula or wooden spoon.
7. Shape cookies: Use a cookie scoop or tablespoon to drop rounded dough balls onto the prepared baking sheet, spacing them about 2 inches apart.
8. Bake: Place the cookies in the preheated oven and bake for 10-12 minutes, or until the edges are golden brown but the centers remain slightly soft.
9. Cool: Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.