Add flour, oil and salt; stir until mixture forms ball.
Place on lightly floured surface; knead until smooth and no longer sticky.
Sprinkle 2 Tbsp. Parmesan onto bottom of 12-inch deep-dish pizza pan sprayed with cooking spray. Press dough onto bottom and 1 inch up side of prepared pan.
Brown sausage in large skillet; drain.
Add onions; cook and stir 5 min. or until tender.
Drain. Stir in tomatoes, tomato paste and oregano; simmer 15 min., stirring occasionally.
Place half the mozzarella on bottom of crust; cover with half the meat sauce. Repeat layers.