Prep veg. Do a rustic chop: tomatoes into wedges; cucumber and pepper into chunky pieces; onion into thin half-moons.
Mellow the onion. Rinse slices in cold water 10–20 seconds; drain well.
Assemble. In a wide bowl, layer tomatoes → cucumber → pepper → onion → olives → capers.
Crown with feta. Place the block of feta on top. Sprinkle oregano and black pepper.
Dress & season. Drizzle EVOO and red wine vinegar. Add salt to taste (go light; feta and olives are salty).
Finish & serve. Toss very gently or serve as is. Add parsley or mint if you like. Eat right away.