AuCoin was born in Portland, Oregon, on October 21, 1942, to Francis Edgar AuCoin, a short order cook from Portland, Maine, and Alice Audrey Darrar, a waitress from Madras, Oregon. When he was four, his father abandoned the family. Les and his brother Leland moved with their mother to Redmond, Oregon, then a small Central Oregon sawmill and farming town, living on her restaurant wages and tips. AuCoin attended Redmond High School, where he was elected most valuable player on the school's basketball team. He also joined the staff of the school newspaper, where he discovered an aptitude for writing—a skill that would help propel him into journalism, Congress and, in political retirement, life as a writer. In 1960, he became the first male in his extended family to graduate from high school.