Cook potatoes in large pot of boiling salted water until just tender. Drain and cool slightly. Cut potatoes into small pieces and place in large bowl.

Meanwhile, heat 2 teaspoons olive oil in heavy medium skillet over medium-low heat. Add onion and saute until translucent, about 5 minutes. Add garlic and cook 1 minute longer. Add onion mixture to potatoes. Add remaining 1/4 cup oil, tomatoes, vinegar, basil and oregano. Toss to combine well. Season salad to taste with salt and pepper.