The marinade is what makes the steak so flavorful. Mix olive oil, oregano, red wine vinegar, and grated garlic in a large bowl. Add the steak and coat it thoroughly in the mixture. Cover and refrigerate for at least 30 minutes, or up to 4 hours for the best results. Remember to bring the steak to room temperature before cooking.
Preheat your grill pan or skillet to medium-high heat. Season both sides of the steak with salt and pepper, then remove any excess marinade. Grill the steak for 5-7 minutes on each side, depending on your preferred doneness. Medium-rare (130°F-135°F) is ideal for juicy meat. Once cooked, transfer to a cutting board and let it rest for 5 minutes to retain the juices.
Slice the rested steak thinly, cutting against the grain to ensure tenderness. This will result in soft, manageable pieces perfect for layering in your gyro bowls.
Arrange warmed pita bread in your bowls or serve as a side. Layer shredded lettuce, thinly sliced onions, tomatoes, and the sliced steak on top. Drizzle with creamy tzatziki sauce for the finishing touch. Feel free to add more of your favorite toppings for a personal twist.