Bring chicken stock to a boil in a large saucepan and stir in the couscous. Cover and remove from heat. Let stand for 5 minutes.
In a large bowl, whisk together the olive oil, lime juice, vinegar and cumin. Add spring onions, capsicum, coriander, corn and beans then toss to coat.
Fluff the couscous well, breaking up any chunks with a fork. Add to the bowl with the vegetables and mix well. Season with salt and pepper to taste and serve at once or refrigerate until ready to serve.