Combine butter and sugars and beat with an electric mixer until creamy. Add egg and vanilla; beat well. Add flour mixture; mix well. Add oats, chocolate chips, cranberries and black walnuts; stir well.
Drop dough by rounded spoonfuls onto ungreased baking sheets.
Bake about 9 minutes, until just golden brown. Let cool 1 minute on baking sheets; remove to wire rack. Let cool completely. Makes about 2 dozen.