To make the dressing, in a large bowl whisk together olive oil, red wine vinegar, Dijon mustard, oregano, and salt and pepper to taste (I like ½ teaspoon salt and ¼ teaspoon pepper).
Add the diced cucumber and the sliced red onion and marinate at least 5 minutes or up to 30 minutes.
To the bowl with the dressing, add the lettuce, tomatoes, chickpeas, and Kalamata olives. Toss to combine and sprinkle with feta cheese.
Video
Notes
Cucumbers: If you use thin-skinned cucumbers, peeling and seeding is optional.
Red onions: Substitute sweet onions if desired. 1 cup of onions may sound like a lot, but you temper the harsh raw flavor after a few minutes of marinade time in the vinaigrette.
Grape tomatoes: 1 ½ cups diced tomatoes may be substituted for the grape tomatoes. Seed your tomatoes if desired.
Kalamata olives: Substitute black olives or your favorite green olives if desired. I prefer to leave them whole, but you can cut them in half or slice them.
Yield: This salad makes 4 generous servings.
Storage: Once you add the dressing, leftovers won't keep well.
Make ahead: The red wine vinaigrette can be made up to 3 days in advance. Store covered in the refrigerator. The vegetables can be prepped the day before and stored separately in the refrigerator.
More mix-ins: Get creative with diced green bell peppers, cubed avocado, whole pepperoncini, or even 8 ounces cooked pasta (drained and cooled).
Make the vinaigrette your own: Try adding 1 tablespoon fresh lemon juice, a teaspoon of honey, a minced clove of garlic, or a pinch of red pepper flakes.