Preheat oven to 350 degrees Fahrenheit.
In the bowl of an electric mixer, cream together butter, brown sugar, granulated sugar, vanilla and eggs. Add peanut butter and mix.
Add salt, flour, baking soda, and oats and mix until combined, scraping down the sides of the bowl with a spatula, as necessary. Mix in chocolate chips and M&M's.
Form or scoop dough into 1 1/2" dough balls and place on a cookie sheet. Press dough balls down slightly with the palm of your hand. Press additional M&M's in the top, then bake for approximately 8 minutes. Don't over bake. Allow the cookies to cool for a few minutes on the pan before removing them to a cooling rack to cool completely.