In a mixing bowl or zip-lock bag, whisk together the 3 tbsp olive oil extra-virgin, 2 tbsp fresh lemon juice from about 1 lemon, 3 cloves garlic, 1 tsp dried oregano, ½ tsp kosher salt, and ¼ tsp black pepper. Add the 1 ½ lb boneless skinless chicken breasts pounded to even thickness, turning to coat evenly. Marinate for at least 15 minutes at room temperature, or up to 4 hours in the fridge.

Preheat your grill or grill pan to medium-high heat. Remove the 1 ½ lb boneless skinless chicken breasts pounded to even thickness from the marinade and shake off any excess. Grill for 6–7 minutes per side, until the internal temperature reaches 165°F and grill marks form. Transfer to a cutting board and let rest for 5 minutes before slicing diagonally.

In a small mixing bowl, whisk together the 3 tbsp olive oil extra-virgin, 2 tbsp red wine vinegar, 1 tsp dried oregano, ½ tsp kosher salt, and ¼ tsp black pepper until emulsified. Taste and adjust seasoning as needed.

In a large mixing bowl, combine the sliced large English cucumber halved lengthwise and sliced into half-moons, 2 cups cherry tomatoes, ½ whole red onion, and 1 whole green bell pepper seeded and chopped into bite-sized pieces. Drizzle the dressing over the vegetables and toss gently to coat.

Transfer the dressed salad to a serving platters (Large) or individual bowls. Scatter the ½ cup Kalamata olives and 4 oz feta cheese crumbled or cut into small cubes over the top. Arrange the sliced grilled 1 ½ lb boneless skinless chicken breasts pounded to even thickness on top and finish with an extra drizzle of olive oil extra-virgin and a pinch of dried oregano if desired. Serve immediately.