Discard any brown or wilted leaves from the romaine. Separate the head into individual leaves. Trim the thick center ribs from the romaine leaves, and tear the rest of the leaf into bite sized pieces. Wash and dry the lettuce, preferably in a salad spinner. The romaine may be cleaned up to a couple of hours before serving; refrigerate it in a serving bowl covered with a damp towel.
Cut the tops and bottoms off the oranges with a paring knife. Trim off the skin, removing as much of the white pith as possible. Remove the sections from between the membranes with a paring knife. Work over a medium bowl to catch any juice from the oranges. Set the orange segments aside in a small bowl.
Whisk the collected orange juice, vinegar, honey, and thyme together. Whisk in the olive oil in a thin stream until blended. Season with salt and pepper, to taste.
Toss the lettuce, onion and olives together with the dressing in a serving bowl. Scatter the orange segments over the salad and serve.