Saute onion in olive oil; add garlic. When onion starts browning, cook garlic slightly; add tomatoes and a dash of oregano. Cook 20 minutes.
Place dough in large sheet cake pan about 3 inches deep. Pour olive oil in bottom of pan and a little on top of the dough; spread dough with fingers starting at center to work out to sides of pan.
Pour pizza sauce on dough, spread all around; add meat, if desired, or mushrooms. Top with about 1 lb. shredded mozerella. Sprinkle with grated Parmesan. Bake at 375 degrees for 45 minutes on middle rack.