Preheat oven to 425°. On a lightly floured surface, roll and stretch dough into a 10-in. circle. Cover; let rest for 10 minutes. Roll and stretch the dough into a 12-in. circle. Grease a 10-in. cast-iron or other ovenproof skillet; sprinkle with cornmeal. Press dough onto bottom and 1 in. up sides of prepared skillet.
Spread with pizza sauce; top with sausage, 1 cup cheese, oregano and green pepper. Sprinkle with remaining 1/2 cup cheese. Bake until crust is golden brown, 20-25 minutes. If desired, sprinkle with red pepper flakes.