Prepare the sauce by whisking together the yogurt, hummus and oregano in a small bowl. Season it to taste with salt and pepper and set it aside. Coat a grill or a ridged grill-pan with cooking spray. Heat it until very hot. Put the vegetables on skewers, one type of vegetable per skewer. In a bowl whisk together the garlic, coriander, cumin, cinnamon, pepper flakes and oil for the marinade. Add the salt and pepper to taste. Pour the marinade into a flat pan or plate big enough to hold the skewered vegetables. Place the skewers in the pan, turning to coat all sides of the vegetables, using a pastry brush, if desired. Grill the vegetables, turning occasionally, until tender. Check frequently. Tomatoes will cook the fastest; the other vegetables will take varying amounts of time. Remove each skewer when it is done. Slide the vegetables off the skewers and into a bowl. Cover the bowl with plastic wrap for 10 minutes, so the vegetables can release their juices and soften. Meanwhile, heat the pita bread, either on the grill for 1 minute or in the microwave for 15 seconds, until warm and soft. Tuck one-fourth of the vegetables into the pocket of each pita. Top it with a quarter of the yogurt sauce and serve.
Yield: 4 servings