1. Preheat broiler.
2. Combine first 3 ingredients in a shallow dish; stir in 1/2 teaspoon salt and pepper. Add halibut, turning to coat; let stand 15 minutes. Arrange halibut on the rack of a broiler pan coated with cooking spray; place rack in pan. Broil 8 minutes or until fish flakes easily when tested with a fork or until desired degree of doneness.
3. Combine remaining 1/8 teaspoon salt, yogurt, cucumber, dill, and garlic in a bowl, stirring well. Spread 1 1/2 tablespoons yogurt mixture in the center of each pita wrap; top each with 1 fillet, 1/2 cup lettuce, 2 tablespoons onion, and 2 tomato slices. Roll up.