Preheat the oven to 350 F. In a large bowl, mix together cake mix, eggs, peanut butter, and vegetable oil until smooth. Fold in M&Ms.
Use a cookie scoop to place the cookies onto a large ungreased baking sheet at least 2-inches apart. Place one Oreo cookie on each cookie dough. Cover with more dough, and bake for 10-12 minutes.