Heat the oil in a medium-sized pot set over medium-high. Add the onion and garlic and cook 2 minutes. Add the stock and citrus juice and zest and bring to a boil. Mix in the couscous, pine nuts and mint. Cover, remove from the heat, and then let stand 5 minutes. Fluff the couscous with a fork to separate the grains and then serve.
Note: To toast the pine nuts, place in a single layer in a baking pan. Bake, shaking the pan from time to time, in a 350 degrees F oven for 10 to 15 minutes, or until lightly toasted.