1. Combine the first 7 ingredients in a large bowl and mix well. Refrigerate for 30 minutes. Can be made the day before and refrigerated over night.2. Preheat Grill to medium high heat.3. Shape mixture into 4 equal patties with your hands.4. Lightly spray Grill grates and grill for 6 minutes on each side or until center is no longer pink.5. Assemble burger with1 pita pocket, feta cheese, onions, spinach and olives.