14 Whole Foods That Start With O

Looking for an extensive list of whole foods that start with the letter O? 

Look no further, we’ve got you covered!

Browse this list of 14 foods that start with O to get some new cooking inspiration, learn more about where each food comes from, and understand the health benefits of each food.

Let’s dive in!

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1. Oats

Oats (Avena sativa L.) are a type of cereal grain and one of the world’s oldest crops (1).

After harvesting, they are dehulled and then processed into one of several forms: rolled oats, steel-cut oats, quick-cooking oats, instant oatmeal, oat flour, or oat bran (2).

Oats are fairly bland on their own. They readily take on the flavor of other foods and pair well with just about anything, especially fruit, nuts, chocolate, and spices.

Regular oat consumption is associated with a lower risk of developing type 2 diabetes, possibly due to a type of fiber in oats called beta-glucan (3).

Feeling bored with oatmeal? Try boosting the flavor (and nutritional value) by cooking the oats in milk, then add a spoonful of nut butter, fresh berries, and some cinnamon.

Don’t forget to try oat milk — a non-dairy alternative to cow’s milk made by blending oats with water, then straining to remove the solids. It’s perfect for lattes! 

2. Octopus

Octopus is a cephalopod, a class of marine animals (including squid and cuttlefish) known for having many arms or tentacles (4).

The octopus tentacles are edible and prized for their mild flavor — slightly sweet and not at all “fishy.”

However, if not properly prepared, octopus can become rubbery. To avoid this, simmer gently in a pot of water for 1-2 hours before using in a recipe. 

A 3-ounce serving of octopus provides 24 grams of protein, 8 mg (44% DV) of iron, and an impressive 30 mcg (1250% DV) of vitamin B12 (5, 6).

Frozen octopus is available at some grocery stores, while you’re more likely to find fresh octopus at specialty fish markets.

3. Okra

Okra, also known as “lady’s finger,” refers to the immature pod of the okra plant, which is native to Africa (7).

This unique vegetable has fuzzy, green skin with edible, white seeds on the inside and a mild, grassy flavor. 

When okra is cooked, it releases something called “mucilage” — a thick, slimy substance made from a mixture of polysaccharides (a type of carbohydrate) (8).

One cup (160 g) of cooked okra provides 5 grams (18% DV) of fiber, 141 mg (11% DV) of calcium, 98 mg (23% DV) of magnesium, and 34 mg (37% DV) of vitamin C (6, 9).

You’ll find fresh, frozen, and canned okra at most grocery stores. Some also carry pickled okra, which is great for snacking.

There are plenty of ways to enjoy okra — try it deep-fried, oven-roasted, sauteed with garlic and tomatoes, or in stews like gumbo. 

4. Olallieberries

The olallieberry is a cross between a loganberry and a youngberry, both related to blackberries and raspberries. 

It resembles an elongated blackberry, with a more intense, tart flavor and a juicy, tender texture.

Olallieberries are mainly grown in California, where you’ll find them at farmers’ markets. Jams and preserves made from olallieberries are also available online.

Use olallieberries the same way you would any other berry — in smoothies, yogurt bowls, oatmeal, or baked goods like muffins and crisps.

5. Olives

Olives are small fruits of the olive tree (Olea europaea), a native of the Mediterranean region and one of the oldest tree species (10).

As they ripen, olives change colors from yellow-green, to light brown, to reddish purple, and finally to dark brown or black (11).

Most harvested olives are used to produce olive oil — made by pressing and grinding green or black olives to extract the oil (12).

Olive oil is a rich source of oleic acid, a type of monounsaturated fat that has been linked with numerous health benefits, including a reduced risk of heart disease (13, 14, 15).

When shopping for olive oil, look for products with a quality seal. This ensures that the oil hasn’t been adulterated or blended with other oils — a common problem in the olive oil industry (16).

Whole olives are available canned, marinated, fermented, or stuffed with things like garlic, pimentos, or cheese. They can be eaten alone or added to salads, pastas, pizzas, and more.

6. Onion

Onions are root vegetables known for their pungent scent and flavor. As members of the Allium family, they are related to garlic, leeks, and shallots (17). 

Onions are bulb-shaped with crisp, juicy flesh covered in dry, papery skin and come in a variety of sizes and colors (red, yellow, and white).

Cutting an onion triggers the formation of a compound called propanethial S-oxide, a gas that can irritate the eyes (18, 19). To avoid this, try wearing onion goggles! (Contact lenses can also reduce the sting.)

Onions are loaded with flavonoids, a group of antioxidant compounds known for their anti-inflammatory and anti-cancer properties (20, 21).

In the produce section, you’ll find red, yellow, and white onions, along with pearl and boiler onions, which are smaller and milder than regular onions.

You can use onions in almost any savory dish, especially salads, sandwiches, pizzas, soups, and salsas. 

7. Opah

Opah, also known as “moonfish,” is a very large fish (weighing an average of 100 pounds) found off the coasts of Hawaii and California (22).

It has dark reddish-pink flesh that turns white when cooked and tastes like a cross between tuna and swordfish (22).

Opah is an excellent source of omega-3’s (DHA and EPA) — it contains 1,350 mg per 3-ounce serving, which is a little less than the amount found in salmon (23, 24).

You can purchase fresh opah at specialty seafood markets in Hawaii and along the west coast of the U.S., while frozen opah is sometimes available online.

Although it can be prepared using almost any method, opah is often grilled and paired with mango salsa, rice, and vegetables.

8. Oranges

Oranges are a popular citrus fruit that originated in Asia and are now grown throughout the world, including in the United States (25). 

There are 3 main types: sweet oranges (good for juicing or snacking), mandarin oranges (best for snacking), and bitter oranges (used in marmalades and liqueurs).

Sweet oranges are juicy and sweet-tart, while mandarin oranges are smaller, sweeter, and easier to peel. Bitter oranges aren’t typically eaten raw due to their intense, sour flavor.

One whole orange (154 g) provides 72 calories, 4 grams (14% DV) of fiber, 82 mg (92% DV) of vitamin C, 279 mg (6% DV) of potassium, and 62 mg (5% DV) of calcium (6, 26).

Navel oranges are available at grocery stores year-round. Other varieties like blood oranges and cara cara oranges are in season during the winter and early spring.

Beyond snacking, oranges can also be added to salads and baked goods, and orange juice is perfect for marinating meats like beef and chicken.

9. Orange roughy

Orange roughy is a deep-sea fish — found mainly off the coasts of New Zealand and Australia — that can live to be 140 years old (27).

It has bright red-orange scales (hence the name) and tender, white flesh with a mild, delicate flavor, similar to tilapia.

Like other white-fleshed fish, orange roughy is very lean, with less than one gram of fat in each 3-ounce serving. It also provides more than 100% of the daily value for selenium (6, 28).

According to the FDA, children and pregnant women should avoid orange roughy due to its high mercury content (29).

Look for fresh or frozen orange roughy fillets at supermarkets, seafood markets, and online. They can be poached, baked, broiled, or fried, and are often served with rice and vegetables.

10. Oregano

Oregano is the name used to describe two unrelated herbs: Mediterranean oregano (Origanum vulgare) and Mexican oregano (Lippia graveolens) (30, 31).

Mediterranean oregano (used in Greek and Italian cuisine) is a member of the mint family and has a bitter, peppery flavor with minty undertones.

Mexican oregano, on the other hand, belongs to the verbena family and is known for having a bolder, more pungent flavor, with hints of citrus and licorice.

Both types of oregano are high in carvacrol, an antioxidant compound that helps protect cells against damage caused by free radicals (31, 32).

Most grocery stores carry fresh and dried Mediterranean oregano (labeled simply as “oregano”). Mexican oregano is more likely to be found at Latin food markets. 

Use oregano to add a depth of flavor to tomato sauces, meat marinades, salad dressings, tacos, beans, and soups.

11. Oroblanco

Oroblanco, which means “white gold” in Spanish, is the name of a hybrid citrus fruit that was developed by crossing a low-acid pomelo with a white grapefruit (33).

Its thick rind ranges in color from bright green to yellow, and its bright yellow flesh tastes like grapefruit, but without any of the bitterness.

Oroblanco is high in naringin, an antioxidant compound that may help lower blood pressure and reduce blood sugar levels (33, 34, 35).

Oroblanco can be difficult to find depending on your location. Look for it at specialty produce stores or consider purchasing online.

Enjoy this refreshing fruit on its own as a snack, or use the juice to sweeten marinades, dressings, and beverages. 

12. Ostrich

The ostrich is the world’s largest species of bird, weighing up to 250 pounds and standing 7 feet tall.

Unlike other poultry, ostrich meat is dark red and tastes more similar to beef. It has very little marbling due to its low fat content. 

A 3-ounce (85 g) serving of cooked ostrich provides 21 grams of protein, 3 mg (17% DV) of iron, 3.7 mg (34% DV) of zinc, and 4.8 mcg (200% DV) of vitamin B12 (6, 36).

Ostrich meat is fairly expensive and difficult to find in the US — look for it at health food stores and exotic meat markets.

Ostrich steaks can be quite dry, so try marinating them before grilling or pan-frying. You can also use ground ostrich in burgers, chilis, and any other recipe that calls for ground beef.

13. Oysters 

Oysters are bivalve mollusks, a family of shellfish that have two shells held together by a single muscle (37). 

They are prized for their unique flavor — salty, buttery, and slightly metallic — and slippery, chewy texture that softens when cooked. 

A serving of 6 raw oysters (84 grams) provides a whopping 33 mg (300% DV) of zinc, a mineral that supports immune function and helps maintain healthy skin (6, 38).

Fresh oysters can be found at seafood markets and some supermarkets. Canned oysters (in oil or water) are available in the canned meat aisle of most stores.

Oysters are delicious served raw on the half shell with a squeeze of lemon, cocktail sauce, or mignonette sauce (made with vinegar and shallots).

Don’t underestimate canned oysters, though! They’re just as tasty and super convenient — enjoy them in soups, stews, casseroles, pastas, and dips.

14. Oyster mushroom

Oyster mushrooms (Pleurotus ostreatus) are one of the most common edible mushrooms in the world after white button mushrooms (39).

They have large, fan-shaped caps that range in color light gray to brown, and white gills underneath. Their flavor is mild and earthy with a hint of anise.

Eating oyster mushrooms regularly may benefit heart health by lowering LDL (bad) cholesterol and reducing blood pressure (39).

You’re most likely to find oyster mushrooms at Asian food markets and health food stores, but they can sometimes be found at traditional supermarkets as well.

They can be used in any recipe that calls for button mushrooms but are especially delicious when pan-fried with butter or olive oil and garlic.

Final Thoughts

From oats to oyster mushrooms, there are plenty of delicious foods that start with the letter O.

We hope this list has inspired you to be adventurous and try some new foods, or to gain a new appreciation for some of the foods you already eat every day. 

Comment below to let us know which of these foods are your favorites, and how you use them in the kitchen!