This recipe makes a massive batch of cookies or bars so it's a go-to for large crowds like parties, picnics and your kids' sports teams. Or, freeze half of it in dough balls for cookie emergencies. If you make large cookies, you might get 6 dozen.
Heat oven to 350°F. Prepare cookie sheets with parchment paper.
In a large mixing bowl with an electric mixer, cream softened butter and peanut butter together.
Add white sugar and brown sugar, beating until well combined. Add baking soda.
Add eggs and beat well.
Pour in the corn syrup and vanilla. Continue mixing until everything is incorporated.
At this point, you should be able to add at least a few cups of the oats and still use your mixer. But once the dough gets too heavy, stop using the mixer and continue adding oats stirring the batter with a wooden spoon. Use your sexy arm muscles.
Stir in the M&M's and chocolate chips.
If you are making bars, spread half of the dough into a 13x9-inch pan. Bake at 350°F for 20-25 minutes or until nice and golden brown. If you take the pan out before they turn golden brown, the middle will not be done.
For cookies, baking time depends on how large you make them. Place on cookie sheet. Using the back of a spoon, gently push down the dough a little bit so that they spread out instead of baking in one mound. Bake at 350° for 12-16 minutes, or until golden brown.
Notes
If you want to use all your cookie dough at once, you can make one 13x9 pan of bars (baking time takes about 20-25 minutes) and at least two dozen large cookies (baking time takes about 12-16 minutes).
Or, you can make two 13x9 pans of bars.
Or, if you only want cookies, you can make at least six dozen large cookies or even a few more dozen if you make them smaller.
If you make really large cookies, you might get 6 dozen instead of 12 dozen cookies.