In a medium bowl, whisk together the dry ingredients: flour, baking soda, cinnamon, and salt. Set the flour mixture aside.

In a large bowl, cream butter with both the brown sugar and granulated sugar until smooth. Add in the eggs and vanilla extract, beating until light and fluffy. Easily done with a hand mixer or in the bowl of a stand mixer set on a medium-high speed.

Slowly add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Stir in the oatmeal, ensuring it’s fully incorporated. Be sure to scrap down the sides of the bowl, to fully incorporate the oatmeal. Then fold in the chocolate chips, raisins, and walnuts.

Drop spoonfuls of cookie dough onto prepared baking sheets. Bake at 375°F for 10-12 minutes, or until the cookies are golden brown around the edges. Remove from the oven and let them rest on the baking sheet for 2-3 minutes before transferring to a wire rack to cool completely.