Wisk all dressing ingredients together and set aside.
Prepare the oranges by cutting off the top and bottom. Use a knife to cut off the rind (vs. peeling with your hands), including removing all the white pith, which is bitter. Cut oranges in 1/3-inch slices, then cut those in half.
Slice the red onion into thin rings. Cut the olives in half. Cut the mint leaves into thin ribbons and/or chop the cilantro. Tear the lettuce into medium pieces; wash and dry.
Toss the lettuce in some of the dressing, then place on a platter. Arrange the oranges in overlapping slices on top of the lettuce. Place the onion, optional preserved lemon and olives on top of the oranges. Drizzle all with the remainder of the dressing. Sprinkle the mint or cilantro on top and serve.
An alternative presentation is to toss all the ingredients (oranges through mint or cilantro) together with the remaining dressing and place on top of the lettuce.