Glenn Klein joined the Extension Service in 1953 as Jackson County 4-H Extension Agent, serving in that capacity until 1960. From 1960 to 1968, Klein acted as a State 4-H Specialist. Finally, from 1968 to 1982, he was a Leadership Development Specialist, a joint appointment with a teaching position in the Extension Ed Program. Klein retired from his Extension Service appointment in 1982.
During his time as the 4-H Extension Agent, Klein, operating in Medford, was responsible for the agriculture and science programs in the county. Most notably, he led the 4-H Teen Council in their 1959 Wagon Trek in celebration of Oregon's Centennial from Jacksonville to Corvallis; the Council was awarded a Freedom's Foundation Medal for the activity.
While acting as the State 4-H Specialist, Klein was responsible for a variety of 4-H programs and activities, seeing the beginning of what is now one of the largest 4-H livestock programs. Klein was also asked by then governor Mark Hatfield to serve as one of two advisors to the Oregon Youth Council.
As a Leadership Development Specialist, Klein was involved in numerous leadership development workshops throughout the state, the most important of which were the training of local committees formed to implement the Oregon Land Conservation and Development Commission and the zoning of the entire State of Oregon.