While you're getting organized, bring a large pot of salted water to a boil—this gives you time to prep ingredients while waiting. Dice the red bell pepper into 1/4-inch pieces, finely dice the red onion into 1/8-inch pieces (smaller pieces help distribute flavor without sharp onion bites), and finely dice the celery. Chop the fresh parsley and set aside. Once the water reaches a rolling boil, add the pasta and cook according to package directions until al dente. This is the perfect time to prep your dressing components while the pasta cooks.
In a large mixing bowl, whisk together the Greek yogurt, mayonnaise, relish, rice vinegar, Dijon mustard, oregano, garlic powder, sea salt, and black pepper until smooth and well combined. I like to use Greek yogurt as my base because it adds protein while keeping the dressing creamy—the combination of Greek yogurt and mayo creates the perfect texture that's neither too thick nor too thin. The vinegar and mustard provide brightness that balances the richness of the mayo.
Drain the cooked pasta in a colander and rinse thoroughly with cold water to stop the cooking process and remove excess starch—this prevents the salad from becoming gummy. Let it drain well for about a minute, then transfer the cooled pasta to the bowl with the dressing from Step 2. Add the diced red bell pepper, finely diced red onion, and celery from Step 1, then gently fold everything together until all the pasta is evenly coated with the creamy dressing.
Transfer the macaroni salad to a serving dish and top with the fresh chopped parsley from Step 1. I find that adding the parsley just before serving keeps it vibrant and fresh rather than letting it wilt into the salad. The salad is best served chilled or at room temperature.