Combine oats, nuts and vanilla and set aside. Combine sugar, cocoa, and evaporated milk in a heavy 2 qt. Saucepan. Bring to a full rolling boil over medium heat, stirring constantly. Continue to boil and stir for 2 minutes. Remove pan from heat and add butter. Stir until butter is melted. Quickly add oat mixture and stir until blended. Drop by teaspoonful onto wax paper. Cool.