Preheat the oven to 180°C (350°F) and line a 9"x9" baking pan with baking pan or grease with non stick cooking pray and set aside.
Place the butter, brown sugar, sugar and peanut butter in a bowl and beat together until light and fluffy with an electric beater.
Add in the eggs and vanilla extract and beat until smooth.
Stir through the oats, flour and baking soda until mixed.
Fold through the M&Ms and chocolate chips and press into the prepared baking pan.
Place in the oven for 20-25 minutes. The outsides will be lightly golden and a skewer inserted will only have a few loose crumbs attached. You want to slightly under bake for soft and gooey cookie bars!