Cook the bacon: Place the chopped bacon in a pan over medium heat. Cook until crispy. Remove from the pan and drain on paper towels. Keep a little of the bacon fat if you like to drizzle over the salad.
Prepare the vegetables: Wash and dry the salad greens. Slice the cucumber, tomatoes, and red onion.
Assemble the salad: In a large bowl, combine the salad greens, cucumber, tomatoes, and onion. Sprinkle the crumbled feta on top. Add the crispy bacon pieces.
Dress the salad: In a small bowl, whisk together olive oil, balsamic vinegar, salt, and pepper. Drizzle over the salad just before serving. Toss gently to coat everything evenly.
Optional extras: Add croutons, toasted nuts, or seeds for extra crunch and texture.