Preheat oven to 325 degrees F.
Grease 9x13" baking pan or 10x15" jelly roll pan.
In large bowl with electric mixer, beat together butter and sugars with paddle attachment, or using a hand mixer.
Add eggs, vanilla, corn syrup, salt, and baking soda and beat until well combined.
Add peanut butter and beat until well combined.
Add oats and flour and mix until combined.
Stir in chips and M&M's by hand. The batter will get pretty thick so use your muscles!
Spread evenly into prepared baking pan.
Bake in preheated oven for 25-28 minutes if using 9x13" pan or 18-22 minutes for jelly roll pan, until top is golden brown. Don't over bake!
Let cool completely.
Cut into squares and enjoy!