Pour 2 cups of water into a medium saucepan and bring to a boil. Add the quinoa and 1 teaspoon of salt, lower the heat, and simmer covered for 15 minutes, until the grains are tender and open (they¿ll have little curly tails). Drain, place in a bowl, and immediately add the lemon juice, olive oil, and 1 1/2 teaspoons of salt.
In a large bowl, combine the scallions, mint, parsley, cucumber, tomatoes, 2 teaspoons salt, and 1 teaspoon pepper. Add the quinoa and mix well. Carefully fold in the feta and taste for seasonings. Serve at room temperature or refrigerate and serve cold.