Graham S’mores Cookie Bars with Chocolate and Toasted Marshmallows

Graham’s S’mores Cookie Bars are a hybrid of chocolate chip cookie bars and classic s’mores, built on a layer of graham crackers and filled with Hershey’s chocolate and plenty of marshmallows. As the bars bake, marshmallows melt and sink into the graham cracker base, then cool to form a crisp, caramelized crust that contrasts beautifully with the gooey chocolate and toasted marshmallow center. A perfect late-summer treat.

I keep a running playlist of new songs I like, and every few listens I find myself adding another track I’ve never heard before — a harmless, repeated cycle. When the urge to bake strikes, though, I trade music for the kitchen. With August winding down, these S’mores Cookie Bars felt like the ideal way to celebrate summer’s last sticky, sweet moments.

I call them Graham’s S’mores Bars for two reasons:

1. They feature an exceptionally crispy graham cracker crust that sets them apart from many other s’mores-style bars.
2. My nephew Graham, who is 14 and proudly “cooks” in the kitchen, devised this recipe — hence the name and the proud family association.

A favorite memory: Graham baked three full pans for a family reunion. A leftover pan warmed in the car after a river rafting trip became an unforgettable post-raft snack — gooey, warm, and perfect after a chilly dip.

You are going to LOVE these s’mores bars

There are countless ways to adapt s’mores flavors into bars or brownies; this version combines Graham’s idea with a chocolate chip cookie bar base to create the ideal texture balance. Highlights:

• Real marshmallows are used, not marshmallow creme, which gives authentic toasted flavor and an ooey-gooey texture.
• Chunks of Hershey’s chocolate and chocolate chips create a rich, melty chocolate interior.
• A full layer of graham crackers forms a crisp, snappy crust on the bottom.
• As the marshmallows melt they seep into the grahams and then harden into a caramelized marshmallow-graham crust — an indulgent contrast to the soft center.

Regular marshmallows behave strangely in the oven: they puff dramatically, then collapse as they cool, leaving a gloriously sticky layer of melted marshmallow. In this recipe that effect is desirable — the mallows melt into the dough and graham layer to create a uniquely gooey, caramelized bottom crust. Expect the bars to be much gooier than typical cookie bars; they’re easiest to eat with a fork right away, or wait until they cool completely for hand-held bars.

Most important ingredients

Nearly everything in this recipe is pantry-stable: graham crackers, marshmallows, chocolate chips, and a few full Hershey bars. A few ingredients and techniques make a big difference:

• Graham crackers, marshmallows, and chocolate — the core s’mores flavors in both chip and bar form.
• Baking soda dissolved in hot water: mixing the baking soda with hot water before adding it to the dough tempers its rising action so the bars bake evenly across the pan instead of forming a tall edge and sunken center.
• Cornstarch: helps keep the bars tender and soft even though they bake for longer as a full pan rather than individual cookies.

How to make s’mores bars

Overview of the process:

Dissolve baking soda in a bit of hot water and set aside. Melt butter and combine with brown and granulated sugar, then beat in the eggs and vanilla. Add the dissolved baking soda, then the dry ingredients: all-purpose flour, cornstarch, and salt. Stir in chocolate chips once the dough has cooled slightly. Press a single layer of graham crackers into the bottom of a parchment-lined 9×13 pan, spread half the dough over the crackers, top with a generous layer of marshmallows and broken Hershey’s squares, then dot with the remaining dough and bake at 325°F until edges are golden and the top is browned. Immediately press additional halved marshmallows and more chocolate on top so they melt into the hot pan. Cool completely for clean slices, or cut warm for an extra-gooey serving with ice cream.

Tips: line the pan with parchment to make removal easier, press the grahams into every corner for a full crust, and don’t overmix the dough — stop when a few flour streaks remain to keep the bars tender.

How to store leftover bars

Keep uncut bars in the pan covered tightly with plastic wrap or an airtight lid to prevent drying. Cut pieces can be stored in an airtight container or resealable bag, removing as much air as possible; they stay best on the counter for 4–5 days. For longer storage, freeze as described below.

Can you freeze them?

Yes. Wrap a whole cooled pan tightly in plastic wrap (two layers) and a layer of foil to prevent freezer burn. For individual servings, flash-freeze cut bars on a baking sheet for 30 minutes, then transfer to a freezer bag with most air removed. Thaw whole pans or individual pieces on the counter until soft; whole pans take a few hours, individual bars about 15–30 minutes.

More fantastic bar recipes

If you love cookie bars, try other variations like classic chocolate chip cookie bars, lemon squares, salted caramel brownies, or raspberry swirl cheesecake bars for a range of textures and flavors in easy, crowd-pleasing formats.