Heat oven to177°C (163°C for dark or nonstick pan). Grease or lightly spray bottom only of 33x23-cm pan.
In large bowl, beat cake mix, oil, walnuts, orange segments, reserved 1/3 cup orange liquid, and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes. Pour into pan.
Bake 35 to 40 minutes or until toothpick inserted in center comes out clean. Cool completely, about 1 hour.
To make pineapple frosting, stir together pineapple, dry pudding mix and orange peel. Gently stir in whipped topping. Spread on cake. Store tightly covered in refrigerator.