Vegetarian burgers arrive at the grocery store fully cooked but frozen. Theoretically, you can eat the frozen patty, but that wouldn't taste good or be good for your teeth. Once thawed, you can eat the vegetarian burger without cooking it, which may come in handy during a power outage. Veggie burgers, by design, are meant to be heated, preferably grilled, to bring out the flavors. Fortunately, grilling a veggie burger takes less than 10 minutes.