Just before you assemble the salad, slice the avocado. Set it to the side so you can scoop the flesh directly onto the arugula salad later.
Put the arugula into a large mixing bowl.
Give the vinaigrette another vigorous shake just in case it needs to be emulsified again.
Pour half of of the dressing over the greens. Save the remainder for pouring on later, if you wish, or for another day.
Toss to coat the arugula with the vinaigrette.
Slice the eggs in half and top the salad with them, then add the red onion slices, and, finally the avocado.
Add more dressing, or salt and pepper, if you wish.
This salad is best enjoyed right away.