Preheat oven to 375 F. Grease a 9x13 pan and set aside.
In a microwave safe bowl met butter. Stir until completely dissolved. Add brown sugar, nuts, cooking oats, flour, baking soda and salt and mix well.
Reserve 1 cup and set aside. Press remaining crust into the bottom of the prepared pan. Press firmly and bake for 10 minutes.
Meanwhile, in a saucepan melt caramels and evaporated milk. Cook over low heat and watch carefully. Stirring constantly. When melted, remove from heat.
Remove crust from oven. Sprinkle with half of m&ms and pour caramel on top. Sprinkle reserved cup of crumb crust on top and remaining candies.
Bake for 20-25 minutes or until golden brown. Cool slightly and refrigerate.