Prepare the vinaigrette: In a small bowl or jar, whisk together the olive oil, lemon juice, minced garlic, Dijon mustard (if using), salt, and pepper until well combined.
Assemble the salad: In a large bowl, combine the chickpeas, beets, and feta. Gently toss to mix.
Add dressing: Pour the vinaigrette over the salad and gently toss again to coat all ingredients evenly.
Garnish and serve: Sprinkle with fresh parsley and a final pinch of black pepper. Serve chilled or at room temperature.