In a medium-sized mixing bowl, combine the chickpeas, halved grape tomatoes, diced cucumber, green bell pepper, chopped parsley, and finely diced red onion. Toss gently to distribute the ingredients evenly.
Drizzle the olive oil and red wine vinegar over the salad. Sprinkle in the cumin, salt, and black pepper. Stir well until everything is evenly coated in the dressing, allowing the flavors to meld.
If incorporating avocado, cut it into small cubes and place them in a separate bowl. Squeeze the juice from half a lemon over the avocado, then gently toss to prevent browning. If omitting the avocado, drizzle 1 to 2 tablespoons of lemon juice directly over the salad and mix thoroughly.
Cover and refrigerate for at least an hour before serving to allow the flavors to fully develop. Serve chilled for a refreshing and vibrant dish.