Bring a large pot of salted water to a boil. Add the macaroni and cook until al dente, about 8 minutes.
Drain the macaroni and transfer to a large bowl. Let cool for 10 minutes.
In a separate bowl, whisk together the mayonnaise, mustard, sugar, vinegar, garlic powder, onion powder, salt, and pepper. Mix until combined.
Add the celery, onion, bell peppers, and parsley to the bowl with the macaroni. Pour the dressing over the macaroni and mix until everything is combined.
Refrigerate for at least 2 hours before serving.
Interesting Facts
Macaroni salad is a popular side dish in the United States.
It can be served cold or at room temperature.
It is often served at picnics, barbecues, and potlucks.
This macaroni salad will keep in the refrigerator for up to 5 days.