Monster Cookie Bars are naturally gluten-free and loaded with oats, peanut butter, chocolate & PB chips, and M&Ms. They require just ONE BOWL for a BIG BATCH, making this the perfect easy recipe when you need a bunch of sweet treats for a party or celebration!
2cups(16-ounce jar) peanut buttercreamy or crunchy
5tablespoonsbutterat room temperature
2 ½teaspoonsbaking soda
18ounces(1 small tub) old-fashioned rolled oats
½cupsemisweet chocolate chips
½cuppeanut butter chips
Position rack in center of oven and preheat to 350°F. Generously butter a 18x13x1-inch rimmed half sheet pan. Set aside.
In a very large bowl (using a spoon or an electric mixer), mix together the eggs and sugars until well-combined. Beat in the salt, vanilla, peanut butter, and butter until smooth. Stir in the baking soda (make sure there aren't any lumps) and the oats, then add the M&Ms, chocolate chips, and peanut butter chips and mix until just combined.
Spread the batter into the prepared baking pan, smoothing the top into an even layer and pressing down firmly. Bake for 16 to 22 minutes or until edges are very light golden brown and center is set. Allow to cool in the baking pan before slicing and serving.
Use exactly 18 ounces of rolled oats (not quick oats). Weigh them with a kitchen scale if you are not just using an entire 18-ounce tub. This recipe previously indicated an equivalent amount of approximately 5 ½ cups, but I no longer recommend using cups because different brands of rolled oats may measure out differently and could result in these cookies overflowing the pan.
Make sure you are baking your bars in a true "half sheet pan" that measures 18 x 13 x 1 inches.
Press the dough firmly into the pan. You are aiming for a packed-down, even layer, but with the edges of the dough pushed down below the edges of the pan. This allows a little room for rising without overflowing.