Oneok, Inc. ONE-oak, stylized as ONEOK, is an American oil and gas midstream operator headquartered in Tulsa, Oklahoma. It provides the oil and gas industry with gathering, processing, fractionation, transportation, and storage services. The company is part of the Fortune 500 and S&P 500. Oneok was founded as Oklahoma Natural Gas Company in 1906, but it changed its corporate name to Oneok in 1980. Wikipedia