How to Make It
Preheat the oven to 450°. Set a rack over a baking sheet and arrange the oregano sprigs in the center.
Rub the salmon all over with 2 tablespoons of the olive oil and season with salt and pepper. Place the salmon skin side up on top of the oregano sprigs and roast for 12 to 15 minutes, until the salmon is just cooked through. Let cool slightly, then discard the oregano sprigs and salmon skin; break the salmon into large pieces.
Meanwhile, in a large bowl, combine the chopped oregano and lemon juice. Gradually whisk in the remaining 1/2 cup of olive oil, then whisk in the olives and season with salt and pepper. Reserve 2 tablespoons of the olive vinaigrette. Add the lettuce, tomatoes, cucumber, red onion and chives to the large bowl and season with salt and pepper. Toss to coat.
Transfer the salad to a platter. Top with the salmon and feta. Spoon the reserved olive vinaigrette over the salmon and serve.