Preheat oven to 425. Wash and thinly slice spinach leaves. Cut tomatoes into 1/4" thick slices; thinly slice mushrooms. In 10" skillet over medium heat, cook mushrooms in olive oil until tender. On ungreased large cookie sheet, unroll pizza dough and press into 14 x 12" rectangle; sprinkle with 2 cups cheese over crust. Top with sliced spinach, tomatoes, and mushrooms. Sprinkle with onions, oregano, pepper and remaining cheese. Bake pizza on bottom rack in oven 12 minutes or until crust is golden. Posted to brand-name-recipes by Meg Antczak on Mar 02, 1998