Preheat broiler. In a small bowl, whisk flour, baking powder, oregano and salt. Stir in water and 2 tablespoons oil to form a soft dough. Turn onto a floured surface; knead 6-8 times. Roll into a 12-in. circle.
Brush bottom of a 12-in. ovenproof skillet with remaining oil; place over medium-high heat. Transfer crust to pan; cook 2-3 minutes on each side or until golden brown. Remove from heat. Spread with pizza sauce; top with pepperoni, mushrooms, olives and cheese.
Broil 3-4 in. from heat 3-5 minutes or until cheese is melted.