Bring the quinoa and water to a boil in a small saucepan over high heat. Reduce heat to medium-low, cover, and simmer until the quinoa is tender, and the water has been absorbed, about 15 to 20 minutes.
Scrape the cooked quinoa into a mixing bowl. Add the garbanzo beans, broccoli, garlic, lemon juice, tarragon, mustard, and olive oil. Stir until evenly mixed. Season to taste with salt and black pepper before serving.
