Onesi was a member of the men's golf team from 2007-10 earning All-CAA honors in each of his four seasons. He was a two-time First Team and a two-time Second Team All-CAA selection and earned Team MVP honors twice. Onesi was a two-time CAA Championship runner-up in 2009 and 2010, named CAA Rookie of the Year in 2006-07 and earned a spot on the CAA 25th Anniversary All-Time team. He won the Delaware State Amateur in 2008 and also took second at the prestigious Eastern Amateur that year. Onesi advanced to match play at the US Amateur Championships held at the famous San Francisco Olympic Club in 2007. He has competed on the PGA Tour-Canada in 2015 and the PGA Tour-Latino America and earned an at-large bid to the NCAA South Central Regional Championship in Oklahoma in 2009. Onesi graduated with a degree in business management with a communications concentration.