Bring a large pan of salted water to the boil. Add the couscous and cook following pack instructions. Meanwhile, cut the peel off the oranges with a small fruit knife, then cut into segments – catching any juice in a large bowl. Set the orange segments to one side.
When the couscous is cooked, drain, then add to the bowl with the orange juice. Add the orange zest and lemon zest and juice, olive oil, harissa, spices, and some seasoning. Leave to cool, stirring every now and then to prevent it from sticking together. Can now be chilled for up to 24 hrs.
Once cooled, add the remaining ingredients, including the orange segments, to the couscous. Gently toss everything together, being careful not to break up the orange too much. Serve at room temperature. Any leftovers can be kept in the fridge for up to 2 days.