Place 14 of the graham crackers in food processor container; cover. Process until finely ground. Add butter and 1/4 cup of the sugar; mix well. Press onto bottom of a 13 x 9-inch baking pan. Coarsely chop remaining 4 graham crackers; set aside.
Mix cream cheese, remaining 1 cup sugar and vanilla extract with electric mixer until well blended. Add eggs; mix until blended. Stir in 1/2 cup of the chopped candy. Pour into crust. Sprinkle with remaining candy, marshmallows and reserved chopped graham crackers.
Bake for 40 minutes or until center is almost set. Cool. Refrigerate 3 hours or overnight.