How to Make It
In a small saucepan, bring the red wine vinegar to a simmer with the sugar. Remove from the heat and add the radish slices. Let stand until cool, about 1 hour.
Meanwhile, in a large saucepan of salted boiling water, blanch the green beans until they are crisp-tender, about 3 minutes. Drain and rinse the beans under cold water until cool. Pat the beans dry and cut them into 1 1/2-inch lengths.
In a medium saucepan, bring 1 3/4 cups of water to a boil. Add the quinoa, cover and simmer over low heat until all of the water has been absorbed, about 12 minutes. Uncover and let stand until cool, about 10 minutes.
In a medium bowl, toss the cucumber with 1/2 tablespoon of the olive oil and season with salt and pepper. In a large bowl, toss the quinoa with the parsley, lemon juice and the remaining 3 tablespoons of olive oil; season with salt and pepper. Drain the radishes and add them to the quinoa, along with the beans, cucumber and feta. Toss well and serve.