Prepare quinoa according to package directions. After cooking, allow to cool, then fluff with a fork. (If serving as a warm, main-dish salad, allow to cool just enough that the basil and spinach won't wilt when added and the cheese won't melt.)
In a large bowl, combine cooled quinoa, tomatoes, spinach, chicken, basil, walnuts, parmesan, and garlic. Stir to combine.
In a small bowl, whisk together lemon juice, olive oil, lemon zest, salt and pepper. Pour over quinoa mixture and stir thoroughly to combine.
Serve immediately or refrigerate, covered, until serving.