Mr Peckauskas is accused of attempting to set fire to the Maryam Mosque.
A man arrested in Laois last year has pleaded guilty to engaging in a terrorist plot to attack a mosque in Galway.
39 year old Karolis Peckauskas of Newfoundwell Road Drogheda in Louth is pleading guilty to a charge of attempting to engage in a terrorist activity or a terrorist-linked activity.
The plea comes after 33 year old Darren Gorman from O'Moore Place in Portlaoise and 35 year old Garrett Pollock of Kilhorne Greene Annalong in County Down both pleaded guilty to the same offence earlier this month.
A fourth man, Charles Flynn who is also 35 from Castlerock Avenue, Castleconnell, Co Limerick, faces the same charge and is before the courts on July 20th.
Mr Peckauskas is accused of attempting to set fire to the Maryam Mosque, Old Cottages, Monivea Road, Galway in an attack aggravated by hatred.
In his last appearance in court he was also accused of having two hatchets, a knuckle duster and a hunting knife in a silver BMW car at O’Moore Place, Portlaoise on November 4.
Peckauskas is also facing a charge of possession of an explosive substance in O'Moore Place on the same date.
Earlier this year he was granted leave to challenge whether he can get a fair trial under the Explosives Act, which he claims contravenes his fundamental human rights.
A stay on the explosives charge has been put in place pending a High Court decision on the challenge.
Peckauskas, Gorman and Pollock will all return before the court on October 5 next for a sentence hearing.
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