Thinly slice the romaine lettuce hearts into ribbons, then wash thoroughly to remove any dirt. Dry well using a salad spinner or paper towels.
Thinly slice the white and pale green parts of the spring onions. Finely chop the dill and mint, discarding the stems.
In a large serving bowl, combine the lettuce, spring onions, dill, and mint.
Crumble the feta into the salad.
In a small bowl, whisk together the olive oil, lemon juice, salt, and oregano until smooth and emulsified.
Pour the dressing over the salad, then gently massage the salad with your hands to help the greens absorb the dressing and soften slightly.
Just before serving, give the salad one final toss with tongs to ensure everything is well mixed and coated with dressing. Serve and enjoy!