In a large mixing bowl, combine the mixed greens, diced avocado, halved cherry tomatoes, and diagonally sliced cucumber.

Incorporate thinly sliced red onion, optionally soaked in cold water for a milder taste.

Sprinkle crumbled feta cheese generously on top.

In a small bowl, whisk together olive oil, lemon juice, salt, and pepper until well combined.

Drizzle the dressing over the salad and gently toss to combine, being careful not to mash the avocado.

Serve immediately for the best freshness and texture.