Start by bringing a large pot of well-salted water to a rolling boil over high heat. Add the high-protein rotini or penne pasta and cook until al dente, about 1-2 minutes less than the package instructions suggest. Once done, drain the pasta in a colander, then rinse it under cold water to stop the cooking process.

While the pasta cools, shred or dice the cooked chicken breast into bite-sized pieces. Chop the cherry tomatoes in half, dice the cucumber, and finely slice the red onion and red bell pepper. Organize all these vibrant vegetables into a bowl for easy access.

In a medium mixing bowl, combine Greek yogurt, mayonnaise (or more Greek yogurt), and lemon juice. Add Dijon mustard, dried oregano, salt, freshly ground black pepper, and olive oil. Whisk everything together until smooth and creamy, adjusting the seasoning to taste.

In a large mixing bowl, combine the cooled pasta, shredded chicken, chopped vegetables, and Kalamata olives (if using). Pour the creamy dressing over the top and gently toss everything together until well-coated.

Cover the salad bowl with plastic wrap or a lid and place it in the refrigerator. Allow it to chill for at least 30 minutes, ideally letting it sit for 2-4 hours for the best flavor.

Before serving, give the salad a gentle stir to recombine any settled ingredients. Taste and adjust seasonings if necessary. Garnish with additional fresh herbs or crumbled feta if desired.