Beat butter or margarine and sugars until creamy. Add eggs and vanilla; beat well. Add combined flour, cocoa powder, baking soda and salt; mix well. Stir in oats and raisins, mix well.
Drop dough by rounded tablespoonfuls onto ungreased cookie sheets. Bake 10 to 12 minutes, until cookies are almost set. Do not overbake. Cool 1 minute on cookies sheets, then move to wire racks. Cool - store tightly covered.