Orzo is a rice-shaped pasta that you can cook and serve in much the same way you do rice. That includes boiling it until the liquid is absorbed, cooking it risotto-style, or by using the pilaf method.
Because it's pasta, you can also cook it via the traditional pasta method where you drain away the excess cooking liquid after it's done.
Like other pastas (and also rice), you can serve it hot or cold, as a side dish, and in casseroles, soups and salads. Orzo usually comes in a basic pale yellow color, but it's also available in the familiar tricolor variety you've seen in rotini (aka corkscrew) and other pasta shapes.
Just remember, orzo isn't a grain. It's a form of pasta, which means it's made from wheat. If you're looking for a gluten-free alternative grain, like buckwheat or amaranth of what-have-you, orzo isn't it.
Orzo Cooking Methods
The Pasta Method: This is the method the package will instruct you to use, and it's the standard cooking method for all pasta—bring salted water to a boil, add the uncooked orzo, simmer for around 10 minutes or until it reaches al dente doneness, then drain the liquid, fluff with butter or olive oil and serve. Easy-peasy, lemon-squeezy.
The Boiled Rice Method: With this method, the orzo pasta is cooked the same way as rice, namely, the pasta and cold water are combined in a saucepan. Bring the liquid to a boil, then lower the heat, cover and simmer until all the cooking liquid is absorbed. Note that you can cook other kinds of pasta this way, in particular long pasta like spaghetti and linguine, so long as you break it up into smaller fragments beforehand.
The Risotto Method: Risotto is made by sautéeing uncooked rice (specifically, a starchy, short-grain type of rice called arborio), in oil, along with some onions and other aromatics, and then cooking it by adding a hot stock, a ladleful at a time, stirring continuously until each ladleful of liquid is completely absorbed before adding the next. Which is exactly how you would prepare orzo (orzotto?) using the risotto method. The risotto method coaxes out the starches in the orzo, making it creamy and velvety.
The Pilaf Method: The pilaf method is a combination of the boiled rice method and the risotto method. First we sauté the orzo in a bit of olive oil (or bacon fat!) along with some chopped onion, then we add hot stock, cover the pot with a tight-fitting lid and then transfer the whole thing to a 350 F oven, where it will cook for about 20 minutes, or until all the liquid is absorbed.
This Turkish-style pilaf with orzo uses a combination of rice and orzo cooked by the pilaf method.
As always, there are numerous variables to cooking orzo, among them the weight of the lid of your pot and how tightly it fits. A heavier lid will hold in more liquid (i.e. steam) than one that is lighter or looser fitting.
Moreover, oven temperatures can vary, and yours might average higher or lower than the temperature it is set to. (Use an oven thermometer to check.)
Orzo is a terrific pasta to include in casseroles and other baked dishes. You'll need to watch out for recipes that say to cook the orzo according to package instructions, and then later instruct you to bake it for 20 to 25 minutes. If you do that, it'll be overcooked, obviously, since the package instructions do not anticipate an additional 20 to 25 minutes of cooking.
An accurate recipe should give a specific boiling time *and* baking time, which, when combined, will produce a properly cooked orzo. Otherwise, plan on boiling it for a shorter time than the package instructions, so that it won't overcook during baking.
Indeed, some recipes (like this Greek beef stew with orzo) will call for uncooked orzo, because it cooks through in the oven thanks to the liquid in the other ingredients (much like no-boil lasagna noodles).
Orzo in Salads
Finally, orzo is a wonderful ingredient to use in salads, and it functions equally well as a rice or a pasta. Just be sure to rinse it, drain well, toss it in olive oil to keep it from clumping, and chill thoroughly before adding it to your salad.
For instance, you could substitute cooked orzo in this chopped vegetable and rice salad, or this Waldorf rice salad, which is a different take on the classic Waldorf. And orzo would be a fabulous ingredient to add to this traditional Greek salad.