HEAT oven to 450ºF.
HEAT oil in medium skillet on medium-low heat. Add onions and sugar; cook 10 to 12 min. or until onions are caramelized, stirring occasionally. Add mushrooms; cook and stir 5 min.
SPRAY baking sheet with cooking spray; sprinkle with cornmeal. Pat pizza dough into 13x9-inch rectangle on prepared baking sheet. Bake 5 min. Meanwhile, mix cream cheese spread, milk and garlic powder until blended.
SPREAD pizza crust with cream cheese mixture; top with mushroom mixture, rosemary and shredded cheese. Bake 10 to 12 min. or until crust is golden brown and shredded cheese is melted.