Preheat your oven to 350°F (180°C) and line a baking sheet with parchment paper.
In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Add the egg and vanilla extract to the butter-sugar mixture and mix until well combined.
In a separate bowl, whisk together the flour, baking soda, cinnamon, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Stir in the oats, chocolate chips, walnuts, and raisins until evenly distributed throughout the cookie dough.
Using a spoon or cookie scoop, drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake the cookies in the preheated oven for 10-12 minutes, or until the edges are lightly golden brown.
Remove the cookies from the oven and allow them to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
Enjoy!
