Heat oven to 350°F. Grease 13x9x2-inch baking pan.
Beat butter, brown sugar and granulated sugar in large bowl until creamy. Add eggs; beat well. Stir together flour, baking soda and salt; gradually add to butter mixture, beating until well blended. Stir in butterscotch chips and nuts, if desired. Spread in prepared pan.
Bake 30 to 35 minutes or until top is golden brown and center is set. Cool completely in pan on wire rack. Cut into bars. About 36 bars.