Combine the spring onions, fresh coriander, ginger, garlic and 2 tablespoons water in a blender and purée.
Heat the oil in a large saucepan over moderate heat. Add the capsicum and cook for 4 minutes or until crisp-tender. Add the spring onion purée and cook for 2 minutes. Add the barley, stirring to coat.
Add the stock, 1/2 cup water, the tomatoes, ground coriander and a pinch of salt, and bring to the boil. Reduce to a simmer, cover, then cook for 45 minutes or until the barley is tender. Remove from the heat and stir in the corn.