1Heat oven to 350°F (325°F for dark or nonstick pan). Generously grease or spray bottom and sides of 13x9-inch pan. In large bowl, beat cake mix, butter and egg with electric mixer on low speed until well mixed.
2Stir in oats until crumbly (use fingers if necessary). Reserve 1 cup cake mixture. Press remaining mixture in pan (use plastic wrap or waxed paper to press mixture if it is sticky).
3In heavy 2-quart saucepan, heat caramels and milk over medium-low heat, stirring frequently, until melted. Pour over chocolate layer in pan. Sprinkle with chocolate chips and pecans. Crumble reserved cake mixture into small pieces; sprinkle over top.
4Bake 24 to 29 minutes or until caramel bubbles along edges and cake mixture on top appears crisp and dry. Run knife around sides of pan to loosen bars. Cool completely, about 1 hour 30 minutes. For bars, cut into 6 rows by 4 rows. Store tightly covered.