Cut the tops off of 4 tomatoes and with a spoon remove the pulp from the inside, to form a bowl. Dice the pulp and half of the remaining tomato (reserve remaining half for the Round 2 Recipe Grilled Margherita Pizza). Dice the mozzarella to measure 1 cup. (Reserve the rest for the Round 2 Recipe Grilled Margherita Pizza.)
In a bowl, combine 2 cups of the orzo (reserve the rest for the Online Round 2 Recipe Orzo Soup with Pork), diced mozzarella, diced tomato, vinegar, olive oil, basil, and salt and pepper, to taste. Divide the mixture among the 4 tomatoes and serve.