Mix margarine, sugar and sweetened condensed milk in large mixing bowl. Add coconut, pecans, and vanilla; mix well, using a sturdy large spoon. Chill until firm enough to handle.
Form into small balls and place on prepared cookie sheets . Chill until very firm.
Melt chocolate chips in top pot of double boiler over simmering water. Using a toothpick, dip balls into melted chocolate. Let cool on wax paper.