Cut cucumbers into thick chunks or half-moons about 2cm wide.
Cut tomatoes into four to six wedges each. Slice red onion as thinly as possible. Soak onion slices in cold water for 10 minutes if you prefer a milder flavor, then drain.
Cut bell pepper into rings about 5mm thick. Remove seeds and white membrane.
Add cucumber, tomatoes, red onion, and bell pepper to a large serving bowl. Toss lightly to combine.
Scatter kalamata olives over the vegetables.
In a small bowl, whisk together olive oil, red wine vinegar, dried oregano, salt, and black pepper until combined. Taste and adjust salt if needed.
Pour dressing over the salad. Toss gently to coat all the vegetables.
Place the feta block on top of the salad. Drizzle a small amount of extra olive oil over the feta and add a pinch of dried oregano on top. Serve immediately.