Prepare the vegetables: Chop the cucumbers, halve the cherry tomatoes, dice the avocados, thinly slice the red onion, and chop the fresh parsley. Place all prepared vegetables into a large mixing bowl.

Prepare the vinaigrette: In a small bowl or jar, whisk together the olive oil, lemon juice, minced garlic, dried oregano, salt, and pepper until well emulsified.

Dress the salad: Pour about three-quarters of the vinaigrette over the vegetables in the large bowl. Gently toss everything together until the vegetables are lightly coated.

Incorporate avocado carefully: Add the diced avocado to the salad mixture. Toss one or two more times very gently to ensure the avocado pieces remain mostly intact.

Adjust seasoning and serve: Taste the salad and add the remaining dressing, or additional salt and pepper, if necessary. Serve immediately for the best texture.