To cook the quinoa, use a ratio of 1:2. 1 cup of quinoa should be cooked in 2 cups of water and will take approximately 20 minutes. I cooked mine in my rice cooker. Let the quinoa cool to room temperature.
Drizzle cooled quinoa with olive oil and a few dashes of lemon juice. Mix until combined. Mix in the onion, tomato, cucumber and feta and stir until combined. Chill in the refrigerator.