In a large salad bowl, with wire whisk or fork, mix lemon juice, oil, salt, and pepper. Add tomatoes, green onions, cucumber, parsley, and mint. Toss to coat. Let tomato mixture stand 15 minutes to allow flavors to blend.
In the meantime, toast pitas and let cool. Break pitas into 1-inch pieces.
Just before serving, toss lettuce and pitas with tomato mixture.