Delicious Steak Sandwiches

• 3 TBS red wine vinegar, divided
• 4 tsp. extra-virgin olive oil
• 1 TBS minced garlic
• 1 tsp. dried oregano
• 12 oz. flank steak, trimmed
• 1/2 tsp. kosher salt, divided
• 3/8 tsp. freshly ground black pepper, divided
• Cooking spray
• 2 TBS plain fat-free Greek yogurt
• 1/4 tsp. Dijon mustard
• 4 (6-inch) whole wheat pitas
• 4 romaine lettuce leaves
• 4 thin red onion leaves
• 1 cucumber, peeled and thinly sliced
• 1 tomato, cut into 8 slices

In a large zip-top plastic bag, combine 2 tablespoons vinegar, 1 teaspoon oil, garlic and oregano. Add steak to bag and seal bag. Turn bag over a few times to allow ingredients to cover steak. Let stand at room temperature 20 minutes, turning once or twice. Heat a grill pan over medium-high heat. Remove steak from bag; discard marinade. Sprinkle 3/8 teaspoon salt and 1/4 teaspoon black pepper evenly over both sides of steak. Coat pan with cooking spray. Place steak in pan; grill 5 minutes on each side or until desired doneness. Remove steak from pan; let stand 10 minutes. Cut steak across the grain into thin slices. In a bowl, combine remaining 1 tablespoon vinegar, 1 tablespoon oil, 1/8 teaspoon salt, 1/8 teaspoon pepper, yogurt and mustard, stirring well with a whisk. Cut off 1/3 of each pita to form a pocket. Arrange 1 lettuce leaf, 1 onion slice, one quarter of cucumber slices, 2 tomato slices and one quarter of steak in each pita; top each sandwich with 1 tablespoon yogurt mixture and serve.