In a large, deep skillet, heat the olive oil. Add the leeks and a generous pinch each of salt and pepper and cook over moderately low heat, stirring occasionally, until softened, 10 to 12 minutes. Add the quinoa and cook over moderate heat, stirring, until dry, about 5 minutes.
Add the broth and water to the skillet and bring to a boil. Cover and simmer over moderately low heat until the quinoa is tender and the liquid has been absorbed, about 20 minutes. Remove the skillet from the heat and let stand for 10 minutes. Fluff with a fork, season with salt and pepper and serve.