Bring pie-crust to room temperature and unfold onto a floured baking sheet. Fold 1/2-inch over the edge of the pan and crimp the edges. Preheat oven to 400°F. Remove the rind from the Brie and cut into small cubes. Cut tomatoes into thin round slices. Slice olives as desired. Spread olive oil over crust and sprinkle with half of the Brie. Add tomatoes and olives. Top with onion, remaining Brie, oregano and Parmesan. Bake approximately 20 minutes, until the crust is crisp and cheeses are slightly bubbling.