Rinse and drain quinoa. Place quinoa in a medium saucepan with water and salt and bring to a boil over high heat. Reduce heat, cover and simmer for ~20 minutes, without stirring. Uncover, fluff with a fork and allow to cool for 10-15 minutes.
Place 2 cups cooked quinoa in a large bowl. Add parsley, mint, tomato and cucumber. Set aside.
In a small bowl, combine olive oil, lemon juice and garlic. Drizzle over quinoa and toss until all ingredients are well coated. Add salt and pepper (and feta cheese, if desired).