Preheat oven to 375 degrees F. Grease 13×9 inch baking pan.
Combine cake mix, eggs, melted butter, brown sugar and vanilla extract in large bowl. Beat at low speed with electric mixer until smooth and creamy (approximately 2 minutes). Stir in butterscotch chips and pecans. Spread in pan.
Bake for 20-25 minutes or until golden brown. Cool completely. Cut into bars.