Although he may appear to be nervous and lacking in confidence, Reg Barclay is a highly talented Starfleet systems diagnostic engineer. Stationed aboard the U.S.S. Enterprise NCC-1701-D from 2366, Barclay had a tendency to spend more time inside the holodeck than in real social situations. Barclay also suffered from severe transporter phobia in 2369, although he seems to have overcome this psychological barrier.

While stationed aboard the new U.S.S. Enterprise NCC-1701-E in 2373, and through a strange turn of events involving the Borg, Barclay was able to meet one of his idols, Zefram Cochrane. By 2376, Barclay's main focus was developing a means of communicating with the missing U.S.S. Voyager crew still stranded in the Delta Quadrant.