It's important to rinse quinoa well before cooking to remove a bitter-tasting resin on the outer hull. To cook, combine 1 cup of well-rinsed quinoa with 2 cups water in a 2-quart saucepan and bring to a boil over medium-high heat. Reduce the heat and simmer about 15 minutes or until the liquid is absorbed.
Spread the quinoa on a baking sheet to cool for 10 minutes.
Meanwhile, whisk lemon juice, oil, garlic, the remaining 1/4 tsp. salt and pepper, tomatoes, cucumbers, parsley and mint; toss well to combine.