Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper and set aside.
In a medium bowl, whisk together 1 ½ cups flour, 1 teaspoon baking soda, and ½ teaspoon salt; set the dry mixture aside.
In a large bowl, beat 1 cup butter (at room temperature), 1 cup brown sugar, and ½ cup sugar with an electric mixer until creamy and smooth, stopping once or twice to scrape down the bowl.
Add 2 large eggs and 1 teaspoon vanilla extract to the butter-sugar mixture and beat until combined.
Add the flour mixture to the wet ingredients and mix until just combined—do not overmix.
Stir in 3 cups oatmeal, ⅓ cup Guittard Butterscotch chips, ⅓ cup white chocolate chips, and ⅓ cup semi-sweet chocolate chips until evenly distributed.
Drop dough by rounded tablespoons onto the prepared baking sheets, spacing cookies about 2 inches apart.
Bake for 10–12 minutes, or until the cookies are lightly golden brown.
Cool the cookies on the baking sheets for 1 minute, then transfer them to a wire rack to cool completely.