Preheat the oven to 350 degrees F, or 375 for high altitude. Prepare baking sheets with cooking spray, parchment paper, or silicone mats.
In the bowl of a stand mixer or a large bowl with a handheld mixer, cream together the butter, brown sugar, granulated sugar, baking soda, and salt. Mix on high speed for 2-3 minutes, until very light and creamy.
Add the eggs and vanilla and mix until completely combined.
Add the flour and graham cracker crumbs and mix until just barely combined. Stir in the chocolate chips and marshmallow bits.
Scoop the dough by heaping tablespoons and roll lightly to smooth. Place at least 2 inches apart on prepare baking sheets.
Bake for 10-12 minutes until just golden on the edges. Let the cookies sit for a few minutes on the baking sheet before removing to a wire rack to cool completely.