• ½ cup all-purpose flour
• 1 tablespoon baking soda
• Pinch of salt
• 5¾ cups rolled oats
• ¾ cup (1½ sticks) cold unsalted butter, cut into cubes
• 1½ cups firmly packed light brown sugar
• 1½ cups granulated sugar
• 5 large eggs
• ¼ teaspoon light corn syrup
• ¼ teaspoon pure vanilla extract
• 2 cups creamy peanut butter
• 1 cup (6 ounces) semisweet chocolate chips
• 1 cup (6 ounces) M&Ms

In a large bowl, whisk the flour, baking soda, and salt together. Add the oats and stir until the ingredients are evenly combined.

In the bowl of an electric mixer fitted with the paddle attachment, cream the butter until smooth and pale in color. Add the sugars and mix on low speed until just incorporated. Do not overmix.

Scrape down the bowl and add the eggs, one at a time, beating until smooth (about 20 seconds) and scraping down the bowl after each addition. Add the corn syrup and vanilla and beat until just incorporated.

Scrape down the bowl and add the peanut butter. Mix on low speed until just combined. Add the oat mixture in three additions, mixing on low speed until just incorporated.

Use a spatula or wooden spoon to fold in the chocolate chips and M&Ms. Cover the bowl tightly and refrigerate for 5 hours.

Preheat the oven to 375 degrees F. Line two baking sheets with parchment paper.

Use an ice cream scoop with a release mechanism to scoop out the dough in 2-tablespoon-size balls onto the prepared baking sheets, 2 inches apart. Bake for 12 to 15 minutes, rotating the pans halfway through the baking time, until the cookies just begin to brown. Let cool on the pans for 8 to 10 minutes before transferring the cookies to a wire rack to cool completely. Cookies can be stored in an airtight container for up to 3 days.