Cook the rotini pasta according to package directions until al dente, usually around 7-9 minutes, then drain and rinse with cold water to prevent sticking and stop the cooking process.

In a large mixing bowl, combine the cooked and cooled pasta with the halved cherry tomatoes, diced cucumber, thinly sliced red onion, diced bell peppers, sliced black olives, and crumbled feta cheese.

In a separate small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, dried oregano, garlic powder, salt, and black pepper until well combined.

Pour the dressing over the pasta and vegetable mixture, tossing gently to ensure all ingredients are evenly coated.

Cover the bowl and refrigerate the pasta salad for at least 30 minutes before serving, allowing the flavors to meld together.

Before serving, give the pasta salad another quick toss and adjust seasonings if necessary, such as adding more salt or pepper to taste.