Osheim was born in Rosholt, South Dakota, to Lawrence C. Osheim and Anna Osheim.[2] He attended high-school in Rosholt graduating in 1937.[2]
He then went to serve in World War II as a Navy Air Corps pilot.[2]
After the war Osheim went to the University of South Dakota to obtain his law degree in 1948.[3][4] He was admitted to the bar February 1848 with ten other graduates.[5] He started practicing law as the city attorney of Watertown, South Dakota, a position he served from 1952 until 1886.[2]