In a large bowl, cream together margarine and sugar until smooth. Beat in eggs one at a time, then stir in the vanilla. Combine flour, cocoa, baking soda, and salt; stir into the creamed mixture until just blended. Mix in walnuts. Drop by spoonfuls onto ungreased cookie sheets.
Bake for 8 to 10 minutes in the preheated oven. Cool for a couple of minutes on the cookie sheet before transferring to wire racks to cool completely.