He became prominent in his local Gaelic Athletic Association, and joined Sinn Féin.
In 1991, Bernard O'Hagan, a Sinn Féin councillor for the Sperrin area of the Magherafelt District Council, was assassinated, and Groogan was appointed as his replacement.
[2] He became the first Sinn Féin Chairperson of Magherafelt District Council, and served a second term starting in 2004.
[3] In 2006, Groogan resigned from Sinn Féin, along with Oliver Hughes, but continued to sit on the council as an independent.
Hughes described their resignations as "purely a domestic issue", but the Sunday Times speculated that they may have been in protest at a lack of internal party democracy.