The crumbly white cheese traditionally used in a Greek salad is feta.
Feta is a Greek brined cheese traditionally made from sheep’s milk, sometimes blended with up to 30% goat’s milk. It is formed into blocks and aged in brine, which gives it a salty, tangy flavor and a soft, crumbly texture.
In a classic Greek salad, feta is combined with tomatoes, cucumbers, onions, olives, and often green peppers. It is usually served in a slab or large pieces rather than finely shredded, then dressed with olive oil and oregano. The salad is commonly called horiatiki, meaning “village salad.”
Ricotta is softer and sweeter, mozzarella is milder and stretchier, and halloumi is firmer and designed to hold its shape when grilled. Similar white brined cheeses exist around the Mediterranean, but feta is the canonical answer for Greek salad. Since 2002, “feta” has been protected as a designation of origin in the European Union.