In 1963, Kraabel began a doctoral degree program in New Testament and Early Christian Literature at Harvard Divinity School.

His research topics centered on the character of Judaism in the Roman Empire and its relevance for the understanding and description of early Christianity.

His service as research assistant to Erwin R. Goodenough, a distinguished scholar in that subject area, both grew out of this interest and nurtured it.

The interest continued in his experience as a field archaeologist, in 1966, for the Harvard-Cornell Archaeological Exploration of the site of ancient Sardis in Turkey.

[6] In the fall semester of 1967, Kraabel began his teaching career as a member of the faculty of the Department of Classics at the University of Minnesota.

In 1988, Luther College named him to an endowed professorial chair, Qualley Professor of Classics, a position he occupied until his retirement.

From 1969-73 Kraabel was associate director, with Eric Meyers of Duke University, of the Joint Expedition to Khirbet Shema', Israel, an archaeological project of the American Schools of Oriental Research.