Chewy peanut butter oatmeal cookies stuffed to the gills with chocolate chips and M&M's. Perfect for creating ice cream cookie sandwiches or dunking into a tall glass of milk!
Heat oven to 350 degrees F. Line cookie sheets with parchment paper or silicone baking mats.
In a large bowl, whisk together flour, oats, salt, and baking soda; set aside.
Using an electric hand or stand mixer, cream the butter and both sugars until well combined, about 2 minutes. Scrape down sides of the bowl. Add the eggs, one at a time, mixing on medium-high speed to incorporate each one completely before adding the next. Add the peanut butter and vanilla extract, then mix on medium speed until well combined, about 1 minute.
Turn mixer to low and add dry ingredients, mixing only until BARELY combined. Over mixing will result in a tough cookie. Use a wooden spoon or spatula to stir in the chocolate chips and M&M's
Bake the cookies for 9 minutes. DON'T OVER BAKE – the cookies should just be set, but still slightly wet on top and very lightly golden around the edges. Let the cookies sit for 1-2 minutes on the cookie sheet before transferring to a cooling rack to cool completely.
Store in a airtight container for up to 4 days (the baked cookies freeze well, also).
Notes
Granulated white sugar can be used instead of powdered sugar, increase the amount to 1 and 1/4 cup.