He served in the United States Army Air Corps as a lieutenant from 1944 to 1945.

He served as First Assistant United States Attorney of the Western District of Oklahoma from 1954 to 1958.

He was President and Chairman of the Board of the Shepherd Mall State Bank in Oklahoma City from 1969 to 1971.

[1] In the 1980s, Cook and other federal judges in his district presided over thousands of cases as the civil docket in Oklahoma swelled due to the region-wide oil bust and savings and loan scandal.

In July 2009, Congressman John Sullivan submitted a bill to rename the Federal building and United States courthouse in Tulsa, Oklahoma, the "H. Dale Cook Federal Building and United States Courthouse.