Place the cooked and drained macaroni in large bowl along with the green olives.
Chop eggs into small pieces and mince the onion. Add to the macaroni.
In a small bowl, combine the mayonnaise, mustard, and vinegar. Stir well and pour over the macaroni. Stir well to coat.
Taste and add salt and pepper, as needed.
Chill in the fridge for at least 1 hour. Stir before serving. Add an extra spoonful of mayonnaise before serving if macaroni seems too dry.
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Notes
This classic macaroni salad is easy to adapt to suit your own tastes. Celery, pickles, and black olives all work well in this dish if you'd like to make additions.