In a small saucepan, bring the vegetable broth to a rapid boil. Once boiling, stir the couscous into the boiling broth and cover the pan with a tight-fitting lid. Remove the pan from the heat and let sit for 5 to 10 minutes, or until the couscous is tender and fluffy. Let cool to room temperature.
While the couscous is cooling, prepare the dressing. In a small bowl, whisk together lemon zest, lemon juice, garlic, salt, and crushed red pepper flakes together. Slowly drizzle in the olive oil and whisk until a thickened dressing forms.
Once the couscous is cooled, add the lemon dressing, tomatoes, cucumbers, onion, olives, peppers, and gently stir to distribute among the salad. Cover and chill for at least 30 minutes before serving.
Transfer the couscous mixture to a storage container and cover and refrigerate for at least 30 minutes to cool. When ready to serve, fluff with a fork, add the feta, parsley, and mint and toss to combine.
