Wash and dry the lettuce leaves (I use this salad spinner). Cut into bite-sized pieces and move to a large bowl.
Add the red onion, grape tomatoes, olives, and salami to the bowl. Mix to combine and set aside.
Add the olive oil, vinegar, oregano, sea salt, and black pepper to taste into a small bottle or jar. Cover with a lid and shake to combine (or use a fork to whisk together). Add to the salad and toss to combine. Set aside.
Cut the buffalo mozzarella into bite size pieces.
Plate the salad and top with the buffalo mozzarella. Season with salt and pepper to taste, if desired, and serve.