Soften butter to room temperature. Preheat oven to 350 degrees.
Cream butter, peanut butter, sugars, corn syrup, vanilla, soda, and salt in a large mixing bowl till very creamy, 2-3 minutes. Add the eggs and mix well.
Stir in M&M's, chocolate chips, and oats till well combined. (Dough will be fairly sticky.) I like to reserve some chips and M&M's to press into the tops of the cookie dough balls before baking.
Form tablespoons of dough into balls and place them onto silicone lined or greased cookie sheets. Flatten cookie dough balls with the palm of your hand.
Bake at 350° for 9-10 minutes.
Notes
There is no mistake, these cookies have no flour.
These cookies don't spread as much as traditional cookies, so you can flatten the dough a bit before baking.
I find that using old fashioned oats is best, the quick oats make a drier cookie.
For large bakery-style cookies, use 2 1/2-3 tablespoons of dough and bake for about 12 minutes.