If you don't have any leftover cooked quinoa, you'll need to cook some of that first. To get the required cup, bring 1 cup of water to a boil. Meanwhile, in a fine meshed sieve, rinse ½ cup of quinoa under running water until it no longer "foams" at the surface.
Add to boiling water, bring back to the boil then lower heat, cover and simmer for about 8-10 minutes, until all the water is evaporated. Allow to cool completely.
In a small mixing bowl, add all the ingredients of the vinaigrette and whisk until well incorporated. Set aside.
Add the rest of the ingredients to a large mixing bowl, pour vinaigrette in and give all that a good stir until all the ingredients are well combined.
Serve immediately or leave in the fridge for a few hours to allow flavors to develop.