"oriental countries" is correct and usable in written English.
It can be used to refer to countries located in the eastern part of Asia, such as China, Japan, South Korea, and so on. For example, "Researchers are studying the cultures of various oriental countries."
The ginseng root has been traditionally used as a sedative in oriental countries.
The rhizomes of Gastrodia elata have been used for the treatment of insomnia in oriental countries.
There is a lack of literature on the association of obesity with low back pain (LBP) in oriental countries.
Although it is beginning to take root in some Oriental countries, art for art's sake remains a Western concept.
Gastrodin, a phenolic glycoside, is the key ingredient of Gastrodia elata, a notable herbal plant that has been used to treat various conditions in oriental countries for centuries.
Officials claimed that the physical isolation would stop the epidemics that they had been led to believe were "prevalent among aliens from Oriental countries".
After giving up her secure life as an Associate Professor in an American university, she arrived in an oriental country full of civil strife.
Long's (1914) article in Ladies Home Journall illustrated the Far Eastern influence on women's fashion well: "…Really this season we are borrowing from almost every Oriental country and the effect is most picturesque: we adapted the Persian lampshade tunic and headdress, the Chinese colors and embroideries, kimono effects and collars from Japan and burnoose draperies from Arabia" (p. 24).
On July 18 , 1830 when the constitution for the Oriental State of Uruguay was approved, the country had scarcely 74,000 inhabitants.
The Cordillera Oriental forms the country's less-rugged eastern spine, separating a narrow coastal plain to the north from a wider belt of rolling lowlands to the south, where most of the country's sugarcane is grown.
