Mix the flour, oats, baking soda, cinnamon, and salt in a small bowl and set it aside.
In another medium-size bowl, cream the butter and sugar together for about 2 minutes until it is light and creamy.
To this, add the eggs and vanilla. At this point, only mix to combine. You don't want to overmix.
Next, add in the flour mixture and mix this one to combine as well.
Last are the raisins and nuts if you are using them. These only need to be mixed to combine them as well.
Cover the dough and let it chill in the fridge for at least an hour, up to 2 days.
When you are ready to bake, preheat the oven to 350 degrees.
Scoop the cookie batter onto your parchment-lined baking sheet and bake for 10-13 minutes. You are looking for the edges of the cookies to be just barely golden brown.
Remove them from the oven and gently move them to the cooling rack. They can be enjoyed hot, warm, or cooled all the way.