Remembered best for his role as Reverend Robert Alden on the popular NBC series Little House on the Prairie, Greer also appeared (as Coach Ossie Weiss) on NBC's mid-1960s sitcom Hank. In addition, he acted in episodes of such Western series as Frontier, Tombstone Territory, and Lawman.
After graduating from Drury University in his home state of Missouri, he was cast as an extra in the 1938 movie Jesse James.
He acted in several episodes of the Adventures of Superman.
He grew up in Anderson, Missouri, as the child of pharmacist Randall Greer and teacher Bernice Dabbs Greer.
He appeared with James Arness in several episodes of Gunsmoke.