Lightly grease a 10 by 15 inch pan and set aside. ( you can also use a large baking sheet, depending on how thick you want your bars).
Combine the oats, rice cereal, chocolate chips, and graham cracker crumbs in a large bowl until well blended. Set aside.
Melt the butter, Nutella, oil, honey, and marshmallows in a large saucepan. Stir well until the mixture is evenly melted and smooth. Add to the dry ingredients and mix until thoroughly combined. ( It can get a little sticky.. I rubbed oil on my hands and mixed it together).
Spread the mixture into the prepared pan, let cool, then cut into bars.
Hint: using a rolling pin will ensure even distribution in the pan. I also used a pizza cutter to cut it into squares :-)