What you need (s’mores material obviously):
Preheat your oven to 350 degrees. Once your oven is preheated lay a graham cracker down, a chocolate piece, and a marshmallow on top. Bake for 4 minutes. You’ll see the marshmallow expand from original size when it’s ready.
Update: I’ve done several oven s’mores (goodbye diet) since I have made these the first time and it was better to put the chocolate on with the second graham cracker after it has cooled for thirty seconds. The chocolate melted much too fast when you put it to bake with the marshmallow.