Preheat the oven to 350F degrees and line 2 cookie sheets with parchment paper or baking mats.
In a large bowl beat the butter, brown sugar and white sugar until fluffy (about 2 minutes). Mix in the peanut butter, followed by the vanilla extract and egg.
Turn the mixer to low speed and beat in the flour, baking soda and salt.
Mix in the oats.
Stir in the chocolate chips and M&Ms.
Form the dough into balls about 3 tablespoons in size (I use a cookie scoop to do this), and place 2 inches apart on the lined cookie sheets. Optionally, place a few extra chocolate chips & candies on top of each cookie.
Bake one cookie sheet at a time in the preheated oven for 12-14 minutes or until the tops look just set.
Cool on the tray for 5 minutes, then transfer to a wire rack and continue cooling.
*Store cookies in an airtight container at room temperature for up to 4 days.