Rinse the quinoa well under running water using a fine-mesh strainer.
Place the quinoa and vegetable broth in a pot over medium heat.
Let it come to a boil, then reduce the heat, cover the pot, and let it cook for 15-20 minutes, or until the quinoa has absorbed all the liquid and becomes tender. Let it cool completely.
Dice the cucumber, tomato, and bell peppers into small cubes. Finely chop the red onion, parsley, mint, and arugula.
In a large bowl, mix the cooled quinoa with the diced vegetables, parsley, mint, and arugula.
In a small bowl, whisk together the lemon juice, olive oil, salt, and black pepper.
Pour the dressing over the quinoa salad and toss the ingredients gently until well combined. Serve immediately.