Line a baking sheet with parchment paper. Set aside.
In a large bowl, stir the brownie mix, eggs, butter, chocolate chips, marshmallows, and graham crackers together until combined.
18 ounces brownie mix, 2 large eggs, ¼ cup unsalted butter, 1 cup chocolate chips, 1 cup mini marshmallows, ¼ cup crushed graham crackers
Tightly cover the bowl of cookie dough and refrigerate for 30 minutes. While the dough is chilling, preheat oven to 350°F.
Once the dough is chilled, scoop a heaping tablespoon worth of brownie dough onto a baking sheet. Repeat to have 6 cookies on a medium baking sheet or up to 12 on a large sheet, leaving at least 2 inches between each cookie.
Bake for 11-12 minutes, or until the edges are set.
Allow cookies to cool on the sheet pan for 5 minutes, then transfer to a cooling rack to cool completely. Repeat with remaining cookie dough.