In a small bowl, whisk together 2 tbs olive oil, 1 tbs lemon juice, 1 tsp minced garlic, 1 tsp dried oregano, 1 tsp salt, and 1/2 tsp black pepper to make the marinade.

Place chicken in a shallow dish or resealable bag and pour marinade over. Turn to coat well. Marinate at room temperature for 15–20 minutes or refrigerate up to 2 hours. If refrigerated, bring to room temperature for 15 minutes before cooking.

Heat a large nonstick skillet or grill pan over medium-high heat. Add a thin film of oil or spray. When hot, add the chicken. Cook undisturbed 4–6 minutes on the first side until golden and a crust forms.

Flip the chicken and cook an additional 3–5 minutes, or until an instant-read thermometer inserted into the thickest part reads 165°F (74°C). Cooking time will vary with thickness.

Transfer cooked chicken to a cutting board and tent loosely with foil. Let rest 5 minutes, then slice thinly against the grain.

Dressing

In a small jar or bowl, combine 3 tbs extra-virgin olive oil, 1.5 tbs red wine vinegar, 1 tsp Dijon mustard, 1 tsp honey or maple syrup, 1/2 tsp salt, and 1/4 tsp black pepper.

Whisk or shake vigorously until the dressing is emulsified and slightly thickened. Taste and adjust seasoning with more salt, pepper, or a touch more honey if desired.

Salad Assembly

In a large bowl, combine 6 cups mixed salad greens, 1 cup halved cherry tomatoes, 1/2 cup thinly sliced cucumber, and 1/4 cup thinly sliced red onion. Toss gently to mix.

Add sliced avocado and sprinkle 1/2 cup crumbled feta and 1/4 cup toasted walnuts or sliced almonds if using.

Drizzle the prepared dressing over the salad (start with about 2 tablespoons and add more to taste). Toss gently to coat the greens without bruising the avocado.

Arrange the sliced chicken breasts on top of the tossed salad. Give a final drizzle of any remaining dressing and finish with a grind of black pepper.

Serve immediately so greens and avocado are fresh.