Grilled Gyro Burgers

Ingredients (8)

• + 2 (8 ounce) containers plain yogurt, divided add to pantry
• + 1 (1 ounce) package dry Ranch-style dressing mix add to pantry
• + 1 cucumber, peeled, seeded, and chopped add to pantry
• ✓ 1 ½ pounds ground beef
• + ¼ cup diced onion add to pantry
• + 6 pita bread rounds add to pantry
• + 2 cups torn lettuce leaves add to pantry
• + 1 tomato, seeded and diced add to pantry