Preheat oven to 350°F and line a baking sheet with parchment paper; set aside.
In a large mixing bowl, mix together cookie dough, M&M’s, peanuts, and raisins with a rubber spatula.
Using a medium cookie scoop or large spoon, portion out cookie dough and place on the prepared baking pan, leaving 2 inches between cookies.
Bake for 10 to 12 minutes until the edges begin to turn a golden brown.
Let the cookies cool on the baking sheet for 2 to 3 minutes, then transfer to a wire cooling rack to cool completely.
Substitute different mix-ins, pretty much whatever you like (see the post for suggestions). Just keep the add-ins to no more than 2 cups. More than that will be difficult to incorporate into the dough.
Try a different variety of cookie dough: peanut butter cookie dough, sugar cookie dough, oatmeal raisin cookie dough, whatever you like.
Make your own cookie dough, if you prefer. Try this recipe for chewy chocolate chip cookies. Omit the chocolate chips and add trail mix ingredients instead.