In a saucepan heat olive oil over medium heat and cook onions until tender. Add orzo and cook for 2-3 minutes. Add olives and 2 cups of chicken stock and bring to a boil. Simmer for 5 minutes and 2 more cups of chicken stock. Return to a boil and pour into a butter baking dish.
Cover with foil and bake at 180ºC or 20 minutes, stirring once. After 20 minutes check orzo and if necessary add more stock and continue to bake until tender. Sprinkle with fresh chopped herbs and serve hot.