Get all veggies washed, chopped ready
Mix the spices, herbs and 1 tablespoon each of salt and pepper with 1 ½ cups of the oil. In a very large bowl, combine all veggies with the seasoned oil. Brush the onion slabs with the seasoned oil.
Light a grill and oil the grate. Working in batches, grill the vegetables over moderately high heat, turning, until tender and charred, 10 minutes per batch. Arrange the vegetables on a platter and keep warm.
In a small bowl, whisk the yogurt with the minced scallions, lime juice and remaining ¼ cup of oil. Serve the vegetables with the yogurt sauce and grilled bread.