Place the skirt steak on a baking sheet. Sprinkle evenly with two pinches of salt on each side. Allow to rest until the salt is absorbed.

If using a propane grill, heat to high. For charcoal, set it up for direct heat grilling and light.

Combine the tomatoes, red onion, olives, the minced oregano, and red wine vinegar in a medium bowl. Sprinkle with salt and pepper and drizzle with the olive oil. Stir to combine, and taste and adjust seasoning if needed. Cover and set aside at room temperature to let the flavors develop.

Season the steak with black pepper. When the grill is very hot, place on the grill. Let cook undisturbed, flipping it only once, until rare. Remove from grill and let rest for 10 minutes. Return it to the grill and warm it through to medium rare or medium (see note).

Slice thinly, across the grain. Top with the salsa, and sprinkle with crumbled feta and remaining oregano.