On a baking pan spread olive oil. Press the pizza dough into the pan until the dough fills pan completely. Cover the dough with a piece of oiled plastic wrap (oiled side down) and allow it to rise, until doubled, up to 1 hour. Scatter tomatoes on risen focaccia. Sprinkle with salt; pepper; oregano; olives and garlic. Set a rack in the lower third of the oven and preheat to 450 degrees. Bake the focaccia for about 25 minutes, or until deep golden. Lift the side of the focaccia with a spatula or pancake turner and check the bottom about halfway through baking time. If it is getting too dark, slide the pan onto another pan to insulate the bottom. To serve immediately, slide the focaccia from the pan to a cutting board. If it will be served later, slide it off the pan onto a rack to cool.