Preheat oven to 350°F. Brush both sides of each pita with 1 Tbsp. olive oil and sprinkle with salt and pepper. Cut pitas into strips about 1 inch wide and 3 inches long. Place pita strips on a baking sheet and bake until golden brown, about 20 minutes.
Whisk lemon juice and 1/3 cup olive oil in a small bowl and season with salt.
Place toasted pita strips in a large salad bowl. Add celery, peas, onion and cucumber. Toss with lemon vinaigrette.
Just before serving salad, gently fold in spinach, feta, mint and parsley. Season with pepper.
