In a bowl, whisk together olive oil, lemon juice, minced garlic, dried oregano, salt, and cracked black pepper. Add the chicken breasts, ensuring they are thoroughly coated in the marinade. Cover and refrigerate for at least 30 minutes.

While the chicken marinates, cook the rotini pasta according to package instructions in a pot of salted water. Simultaneously, bring another pot to a boil and add the quinoa. Cook for around 15 minutes, or until fluffy. Drain the pasta and set aside to cool.

Preheat your grill over medium-high heat. Grill the marinated chicken for approximately 5-6 minutes on each side, until golden brown and cooked through. Let it rest for a few minutes before slicing.

While the chicken rests, slice the cucumbers, halve the cherry tomatoes, and slice the olives. Finely chop fresh parsley or dill for garnish.

In a large mixing bowl, layer the cooked rotini pasta and quinoa as a base. Arrange the sliced grilled chicken, cucumbers, cherry tomatoes, and olives for presentation.

Drizzle tzatziki sauce over the salad and sprinkle the chopped herbs. Serve immediately and enjoy.