Wash cucumbers, sweet bell peppers, red onion, and parsley under cold water. Chop cucumbers into bite-sized pieces, slice bell peppers into strips or chunks, and finely dice the red onion. Roughly chop the parsley.

In a small bowl, combine olive oil and lemon juice. Whisk vigorously until emulsified. Season with salt and pepper.

Pour the dressing over the chopped vegetables in a large bowl and gently combine without mashing.

Toss the salad gently and transfer to an airtight container. Chill in the refrigerator for at least 30 minutes.

Serve the salad cold, giving it a final toss before transferring it to a serving platter.