AuCoin has had a lasting impact on environmental policy in Oregon, authoring and supporting numerous environmental measures while in office. During the 1980s in particular, AuCoin helped pass a number of bills that increased environmentally protected areas in the state. In 1980, he helped declare Cascade Head, a 9,670-acre forest southwest of Portland, a National Scenic Research Area. With Representative Jim Weaver and Senator Mark Hatfield, AuCoin also co-authored the Oregon Wilderness Act of 1984, which designated 930,400 acres of land as protected wilderness and 156,900 acres as the Cascades Recreational Area. In 1986, he supported the Columbia Gorge Scenic Protection Act, making the Columbia Gorge the second US National Scenic area. AuCoin co-authored the 1988 bill which quadrupled the number of officially recognized National Wild and Scenic Rivers in Oregon, and in 1990 he supported a bill to expand the list to include a segment of the Klamath River. Collectively, these efforts created environmental protections for over a million acres of land in Oregon.