Greg earned a BA in political science at Iowa in 1972 and an MD at Iowa in 1976. He received additional medical training at Harvard University. He was a successful plastic surgeon in Des Moines until he challenged and defeated incumbent U.S. House member Neal Smith in 1994. Greg was reelected to the House in 1996, 1998, and 2000, before stepping down to challenge incumbent U.S. Senator Tom Harkin in 2002. After that campaign he resumed his plastic surgery practice. He has volunteered his skills to help hundreds of children in Mexico, Guatemala, Peru, Armenia, and Vietnam by surgically correcting birth defects like cleft lips and palates.