Prep the Chicken: Pat the chicken dry with paper towels. In a bowl, whisk olive oil, garlic powder, smoked paprika, oregano, salt, pepper, and lemon juice. Add chicken and toss to coat.
Let it sit 15–30 minutes at room temperature, or up to 8 hours in the fridge.
Heat the Grill: Preheat a grill or grill pan over medium-high heat. Lightly oil the grates to prevent sticking. If using a skillet, preheat with a little oil until shimmering.
Grill: Grill chicken 5–7 minutes per side, depending on thickness, until the internal temperature reaches 165°F (74°C).
Let it rest 5–10 minutes, then slice against the grain.
Make the Dressing: In a small bowl, whisk yogurt, olive oil, lemon juice, Dijon, garlic, and honey. Season with salt and pepper. Add water a splash at a time until it’s pourable but still creamy.
Assemble the Salad Base: In a large bowl or platter, add mixed greens, tomatoes, cucumber, bell pepper, and red onion.
Toss with a light amount of dressing to coat the greens.
Add Toppings: Layer on sliced grilled chicken and avocado. Sprinkle with feta and nuts or seeds if using.
Finish and Serve: Drizzle a little more dressing over the top. Add a pinch of salt and pepper and a squeeze of lemon if you like.
Serve immediately.