Heat oven to 350°F. Grease bottom only of 8x4 or 9x5-inch loaf pan. In large bowl, combine sugar and margarine; blend well. Add eggs; beat well. Stir in buttermilk.
Lightly spoon flour into measuring cup; level off. Add flour, cocoa, baking powder, baking soda and salt; stir just until dry ingredients are moistened. Stir in nuts. Pour into greased pan.
Bake at 350°F. for 55 to 65 minutes or until toothpick inserted in center comes out clean. Cool 15 minutes. Remove bread from pan. Cool 1 hour or until completely cooled. Wrap tightly and store in refrigerator.