Onions, Tomatoes, Tzatziki. Contrary to the US public's perception the Gyro in Greece is made with Pork. In the US the Chicago Lamb & Beef Gyros, is up to 99% ground Beef & up to 20% Lamb including grain fillers. Thelo is one of 3 known restaurants in the US, that due to religious restrictions, makes 100% Lamb Yeero.