In a large mixing bowl, whisk together the dry ingredients (flour, soda, cinnamon and salt). Set aside.
In a large mixing bowl of a stand mixer, beat butter for 30 seconds. Gradually add brown sugar and beat until fluffy and light in color.
Add egg and vanilla and mix until smooth.
With the mixer speed on low, mix in the dry ingredients.
Stir in oats, raisins and chocolate chips.
Cover the top of the bowl with saran wrap and chill for at least 2 hours or overnight.
Preheat the oven to 350 degrees F.
Line baking sheet with parchment paper or silicone baking mat.
Scoop the cookie dough onto the sheet. I used two scoop of a medium (1,5 tablespoon) cookie dough scoop per cookie.
Bake 12 to 15 minutes. The cookies will look slightly underdone in the middle yet browned on the edges. Let them cool on the sheet for 5 minutes. They will continue to bake.
Transfer onto a wire rack to cool completely.