In a small saucepan, bring quinoa and water to a boil. Reduce heat; cover and simmer about 15 minutes, until quinoa is tender and liquid is absorbed. Transfer to a large bowl, fluffing occasionally to let steam out. Mix in garbanzo beans, lemon juice, olive oil, and salt. Once quinoa mixture has cooled to room temperature, mix in tomatoes, parsley, onion, and feta. When ready to serve, top with slices of avocado. Store leftovers in fridge for up to a week. (Coat any leftover sliced avocado with lemon juice to prevent browning.)
Per main dish serving: 512 calories, 25 grams fat (9 grams saturated fat), 55 grams total carbohydrates, 979 milligrams sodium, 50 milligrams cholesterol, 114 grams fiber, 21 grams protein.