In a mixer, combine margarine, sugar and mix well. Add eggs and beat until creamy. Add flour 1 cup at a time and mix until smooth. Pour into two greased bread loaf pans. Bake at 350 degrees for 1 hour and 15 minutes. Test with a toothpick for doneness. Cool for 10-15 minutes. Use a knife to loosen the edges and dump on to cutting board to slice.