Combine cumin, coriander, cinnamon and cayenne pepper. Whisk olive oil, white wine vinegar, blend with spice blend in medium bowl. Place drained white beans in large bowl and mix in enough vinaigrette to coat. Let stand 10 minutes to allow flavors to blend.
Add tomatoes, cucumbers, feta cheese, red onion, and parsley to white beans. Mix in enough vinaigrette to coat. Season bean salad to taste with salt and pepper. Fill pita halves with bean salad and top with dollop of yogurt. Place 2 pita halves on each of 4 plates; pass remaining vinaigrette separately.