1. Cook the Pasta: Bring a large pot of salted water to a rolling boil. Add the whole wheat rotini and cook according to package directions until al dente. This usually takes about 10-12 minutes. The pasta should be tender but still have a slight bite.

2. Drain and Cool the Pasta: Once cooked, drain the pasta thoroughly in a colander. Rinse it under cold water to stop the cooking process and cool it down quickly. This prevents the pasta from becoming sticky and ensures your salad will be cold. Let it drain well.

3. Prepare the Vegetables: While the pasta cooks, chop your cherry tomatoes, cucumber, red onion, and bell pepper. Aim for similar-sized pieces for an even distribution of flavors and textures in each bite. Finely chop the fresh parsley.

4. Whisk the Dressing: In a small bowl, combine the olive oil, red wine vinegar, Dijon mustard, dried oregano, and garlic powder. Whisk vigorously until the dressing is well combined and slightly emulsified. Season with salt and black pepper to taste.

5. Combine All Ingredients: In a large mixing bowl, add the cooled pasta, shredded or diced cooked chicken, and all the chopped vegetables (cherry tomatoes, cucumber, red onion, bell pepper, and fresh parsley).

6. Dress the Salad: Pour the prepared dressing over the pasta and chicken mixture. Toss gently but thoroughly to ensure all ingredients are evenly coated with the dressing.

7. Chill and Serve: For the best flavor, cover the bowl and refrigerate the pasta salad for at least 30 minutes before serving. This allows the flavors to meld beautifully. Give it another quick toss before serving.