Thread 3 marshmallows alternating with 2 brownies onto each skewer.
Preheat grill to medium. Place a well-greased foil pan or sheet of foil on grill. Grill skewers on foil until marshmallows are golden brown and starting to melt, 15 to 30 sec. per side. (The marshmallows will melt and brown very quickly.) Remove skewers from grill.
In a microwaveable bowl, microwave the caramel sauce on HIGH until warm, about 30 sec. Pour caramel sauce on top of each skewer. Sprinkle graham cracker crumbs on top of caramel.