In a saucepan, combine the potato and enough cold water to cover. Bring to a boil, salt the water and cook until firm-tender, 3 to 4 minutes. Drain.
In a bowl, combine the shallot, garlic, lemon juice, lemon zest, vinegar, mustard, oregano and crushed red pepper. Whisk in about 1/3 cup EVOO to combine. Stir in the olives.
Preheat a grill pan or griddle over medium-high heat. Drizzle the meat with EVOO and rub all over; season with the rosemary, salt and pepper. Add to the pan and cook, turning once, for about 8 minutes for medium-rare. Let the meat rest for a few minutes, then slice on an angle.
Meanwhile, in a nonstick skillet, heat the remaining EVOO over medium-high heat. Add the potato cubes, season with salt and pepper. Cook until browned, 3 to 4 minutes. Flip the potatoes and add the onion and frying (or bell) pepper; cook for 5 minutes. Transfer to a bowl; reserve the skillet. Add the romaine (or arugula or spinach), tomatoes and parsley to the hash.
Meanwhile, add the dressing to the reserved skillet and heat for a minute. Pour over the salad and toss to coat. To serve, arrange the salad on plates; top with the feta, steak and pepperoncini.
