Heat oven to 425°F. Grease cookie sheet. Unroll dough onto greased cookie sheet. Starting at center, press out dough to form 12x8-inch rectangle. Bake at 425°F. for 7 to 9 minutes or until light golden brown.
Meanwhile, in medium bowl, combine chicken, 1/4 cup of the salad dressing, mayonnaise and onions; mix well.
Remove crust from oven. Spread chicken mixture evenly over partially baked crust. Sprinkle with cheese. Return to oven; bake an additional 6 to 8 minutes or until cheese is melted and crust is deep golden brown.
Meanwhile, in large bowl, combine lettuce, chow mein noodles, mandarin orange segments and remaining 1/2 cup salad dressing; mix well. Top each serving with salad mixture.