Cook the quinoa according to the package directions. Transfer to a plate or rimmed baking sheet and refrigerate until cool.
Cook the edamame according to the package directions.
Meanwhile, whisk together the tahini, lemon juice, ginger, honey, ½ cup water, ½ teaspoon salt, and ¼ teaspoon pepper in a small bowl.
Divide the watercress, beets, radishes, edamame, and quinoa among plates and drizzle with the dressing.