|Place of birth||Dublin, Ireland|
|1983–89||St. Patricks Athletic||83||(2)|
|1978–1979||Republic of Ireland||8||(0)|
|1979–1986||League of Ireland XI||?||(1)|
|* Senior club appearances and goals counted for the domestic league only
He played for Shamrock Rovers, Bohemians, VfB Lübeck, Dundalk, St Patricks Athletic and Kilkenny City during his career. He made 180 league appearances and 15 European appearances for Bohs during his 8 seasons at Dalymount Park after signing for Bohs in 1972. He left Bohs in 1980 and had a short spell at VfB Lübeck in Germany before returning to Ireland the following year where he joined Dundalk. While at Oriel Park, he added a third league winners medal. Eamonn moved to St. Pats during the 1983/84 and stayed there until 1989, apart from a short spell on loan at Shamrock Rovers in 1987/88. After Pats, he wound down his playing career as player/manager at Kilkenny where he made 16 league appearances.
He won 9 full international caps for Ireland after making his debut against Poland in 1976.  All of his caps came while at Bohemians.
Gregg has managed Kilkenny City (1989–90), Bohemians (1990–1993) and Shelbourne (1994). He joined Kilkenny as player/manager in 1989 and brought renowned coach Maurice Price with him. The pair led "The Cats" to their best ever league position up to that point. This was noted by the hierarchy at Bohs and in May 1990, he was offered the managers job at Dalymount and he duly accepted. While at Bohs, he won the FAI Cup and came agonisingly close to ending the club long spell without a league title when Bohs lost the league title on a play-off in 1992/93. He never recovered from that disappointment and by December of that year, he was gone from Bohemians. Gregg's next port of call was Shelbourne in January 1994 but his time at the club was a failure and he was sacked in November 1994.
The Gregg name is synonymous with Shamrock Rovers. His two great uncles, 'Jemmer' (real name Michael James) and John were original founder members of the club and his uncle Podge (real name Patrick) won the FAI Cup with Rovers in 1945. His brother Jimmy also played for Rovers in the 1970s. Podge's son in law Mick Gannon won the FAI Cup with Rovers in 1978 and his son Karl Gannon also played for the Hoops in the 1990s.