Spray oil
4 whole grain pita breads
1/2 cup low-fat (1%) milk
3/4 pound lean ground beef
3 tablespoons grated onion
3/4 teaspoon dried oregano
1/4 teaspoon ground allspice
1/4 teaspoon freshly ground black pepper
1/2 teaspoon fine sea salt, divided
3/4 cup Greek yogurt
1/2 cup grated peeled seedless cucumber
1 tablespoon lemon juice
1 tomato, diced
1 cup finely sliced romaine lettuce