Combine first 3 ingredients. Sprinkle evenly on chicken; cover and chill until ready to cook.
Heat 2 tablespoons olive oil in a large tagine or Dutch oven over medium-high heat. Brown chicken, in 2 batches, adding more oil if necessary. Return all chicken pieces to tagine, and top with onion and next 5 ingredients.
Combine saffron and 3/4 cup water; pour over chicken. Bring to a boil. Reduce heat, cover, and simmer 30 minutes or until chicken is done, stirring halfway through cooking time.
Stir in olives and Preserved Lemons; cook 5 minutes or until heated. Serve with hot cooked couscous, if desired.