In a large bowl, dissolve yeast in warm water. Add sugar; let stand for 5 minutes. Add oil and salt. Add 1-1/2 cups flour and cornmeal; beat until smooth. Stir in enough remaining flour to form a soft dough.
Turn onto a floured surface; knead until smooth and elastic, about 4-5 minutes. Place in a greased bowl; turn once to grease top. Cover and let rise in a warm place until doubled, about 1 hour.
Punch dough down; let rest for 5 minutes. Divide into two portions, one slightly larger than the other. On a lightly floured surface, roll out larger portion to a 12-in. circle. Press onto the bottom and up the sides of a greased 10-in. ovenproof skillet.
Preheat oven to 375°. In a large skillet, cook sausage, green pepper and onion over medium heat until meat is no longer pink. Add garlic; cook 1 minute longer. Drain. Stir in mozzarella cheese, pepperoni, Parmesan cheese and oregano. Add to prepared crust.
On a lightly floured surface, roll remaining dough into an 11-in. circle. Place over pizza; seal edges. Cut four slits in top. Bake 30-35 minutes or until crust is golden brown. Spread with tomato sauce.