Heat oven to 350°F (325°F for dark or nonstick pans). In large bowl, beat butter, sugar, cinnamon and egg with electric mixer on medium speed until creamy. Stir in cake mix and oats until blended. Stir in butterscotch chips and walnuts.
On ungreased cookie sheets, drop dough by rounded teaspoonfuls about 2 inches apart. Flatten dough slightly with fingers.
Bake 10 to 12 minutes or until light brown. Immediately remove from cookie sheets to cooling racks. Store covered.