Oscar Crabtree grew up in western Massachusetts and was a 1935 graduate of Chicopee High School. He majored in animal husbandry at the Stockbridge School of Agriculture, and at the University of Massachusetts in Amherst.

He devoted his life to breeding livestock, most notable Guernsey and Holstein dairy cattle in conjunction with managing farm estates. In 1960, Mr. Crabtree became manager of F.W. McCann's Golden Harvest Farm in Roxbury and Bridgewater, whose Guernsey herd exceeded 300. In the following 25 years, the Golden Harvest Farm gained international recognition for production and show winnings.

During his career, Oscar served on the Livestock Advisory Board of the Eastern States Exposition, the Massachusetts Governor's Counsel on Agriculture, and the Advisory Board of the Norfolk County Agricultural School in Walpole, Massachusetts. He also held offices in various state and New England livestock and farm organizations.