Pat chicken breasts dry with paper towels. In a shallow dish, combine chicken with 1 tbsp olive oil, dried oregano, 1/4 tsp garlic powder, salt, and black pepper. Toss to coat evenly. Marinate for at least 10 minutes at room temperature, or up to 30 minutes in the refrigerator.

Preheat a grill pan or outdoor grill to medium-high heat. Lightly grease the grates if needed.

Grill chicken for 6-8 minutes per side, or until the internal temperature reaches 165°F (74°C) using a meat thermometer. Cooking time will vary based on thickness.

Remove chicken from the grill, tent loosely with foil, and let rest for 5 minutes before slicing into bite-sized pieces or strips.

In a small jar with a lid or a small bowl, combine 3 tbsp extra virgin olive oil, fresh lemon juice, Dijon mustard, honey or maple syrup, dried dill, 1/4 tsp garlic powder, salt, and black pepper.

Secure the lid and shake vigorously, or whisk until the dressing is thoroughly combined and emulsified. Taste and adjust seasonings as needed.

In a large mixing bowl, combine the mixed greens, fresh blueberries, thinly sliced red onion, and crumbled feta cheese.

Add the sliced grilled chicken to the bowl.

Drizzle the salad with about half of the lemon-herb vinaigrette. Toss gently to coat all ingredients evenly. Add more dressing to your preference.

Divide the Chicken Blueberry Feta Salad among four plates. If using, sprinkle with toasted pecans or walnuts before serving.