Watermelon Arugula and Pine Nut Salad

  tablespoons fresh lemon juice3 tablespoons balsamic vinegar2 tablespoons fresh oregano, chopped1 teaspoon salt6 tablespoons olive oil9 cups cubed seeded watermelon, drained18 cups baby arugula1 cup pine nuts1 cup crumbled fetaCoarsely ground black pepper to tastesalt to taste1. Whisk together lemon juice, vinegar, oregano, and salt in a large bowl, then add oil in a slow stream, whisking until emulsified.2. Add watermelon, arugula, and pine nuts and toss to coat, then sprinkle with cheese, pepper, and salt.