Place salad greens in a large bowl. In a small bowl, whisk oil, vinegar, mustard, garlic, sugar and oregano until blended. Pour over salad greens; toss to coat. Transfer to a large platter. Arrange tomato slices over greens. Top with basil, pine nuts, onion and cheese. Serve immediately.
To toast nuts, bake in a shallow pan in a 350° oven for 5-10 minutes or cook in a skillet over low heat until lightly browned, stirring occasionally.