In a small bowl, dissolve yeast in warm water. In a large bowl, combine oil, salt, sugar, yeast mixture and 1 cup flour; beat on medium speed until smooth. Stir in enough remaining flour to form a stiff dough.
Turn dough onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover with plastic wrap and let rise in a warm place until doubled, about 1 hour.
Preheat oven to 425°. Grease a 13x9-in. baking pan. Punch down dough; divide into three portions. On a lightly floured surface, combine two portions of dough and roll into a 15x11-in. rectangle. Transfer to prepared pan, pressing onto bottom and up sides of pan. Top with 2 cups mozzarella cheese and 2 cups cheddar cheese. Sprinkle with flour, seasonings, cooked sausage, mushrooms and pepperoni.
Roll out remaining dough into a 13x9-in. rectangle. Place dough over filling, crimping edges to seal; prick top with a fork. Sprinkle with remaining cheeses. Bake on a lower oven rack 10 minutes.
Reduce oven setting to 375°. Spread pizza sauce over cheese. Bake 30-35 minutes longer or until edges are lightly browned. Let stand 10 minutes before cutting. If desired, sprinkle with Parmesan cheese.
Freeze option: Freeze cooled baked pizza pieces in a resealable freezer container. To use, reheat on a baking sheet in a preheated 375° oven until heated through.
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