Place the red onion in a small bowl and cover with cold water. Let sit at least 5 minutes, then drain (this removes some of the harsh bite).
In a small bowl or liquid measuring cup, stir together the dressing: olive oil, red wine vinegar, garlic, salt, oregano, and black pepper.
Place the romaine in a large bowl and drizzle lightly with the dressing. Toss to coat.
Add the cucumber, cherry tomatoes, bell pepper, black olives, capers, and drained red onion. Drizzle with a little more dressing then toss gently to combine.
Last, add 3/4 of the feta, and toss very gently. Add salt and pepper to taste. Sprinkle the remaining feta over the top. Divide between serving bowls and serve with additional dressing as desired.
Notes
TO STORE: Refrigerate leftover salad in an airtight storage container for up to 2 days.
TO MAKE IN A MASON JAR: Layer rinsed and drained canned chickpeas at the bottom of a mason jar with some dressing, followed by the olives, feta, crunchy veggies, and finally the lettuce. Dump the salad into a bowl when you’re ready to eat and toss to distribute the dressing.