In a bowl wash quinoa in at least 5 changes cold water, rubbing grains and letting them settle before pouring off most of water, until water runs clear and drain in a large fine sieve.
Pour 1½ cups quinoa and 2½ cups water into a large pot. Bring water to a boil, then reduce to a simmer and cover pot with lid. Cook 10-15 minutes until all water absorbs and quinoa is fluffy.
While quinoa is cooking, in a small bowl toss beans with vinegar and salt and pepper to taste.
Transfer quinoa to a large bowl and cool. Add beans, corn, peppers, leeks, and coriander and toss well.
For the dressing: In a small bowl, whisk together lime juice, salt, cumin and oil.
Drizzle dressing over salad and toss well with salt and pepper to taste. Serve cold, or at room temperature.