Early in his career Barret produced many oil paintings of classical scenery, often incorporating mythological figures.
There is no evidence that Barret ever travelled to Italy and his name does not appear in John Ingamells listing of British Travellers to Italy.
Most, if not all, of these paintings appear to have been commissioned for houses in Ireland and Barret does not seem to have painted Italianate paintings after he left Ireland.
Thomas Bodkin considered that the oil paintings of Tivoli in Italy which had been attributed to him, to be more likely to be work of his son George Barret junior.
who also produced many paintings with classical themes.
However, these paintings can now be securely attributed to the elder Barret.
 
A source of Barret's earliest landscape paintings came from the re-working of engravings of classical Italianate scenes of artists such as Claude Lorrain.
A pair of paintings sold in 2013, came from the collection of the Rev. Samuel Madden (1686–1765).
Madden established a series of prizes at Trinity College, Dublin, to reward agricultural and artistic enterprise, designed an important landscape garden on the shores of Lough Erne, founded the Dublin (later Royal) Society, and left an important collection of 17th- and 18th-century Italian pictures to Trinity College.
These two paintings were based on engravings of two paintings by  Claude Lorrain.
One of these is after Landscape with a rural dance, which belonged to the Duke of Kingston.
The second is a Landscape with Argus guarding Io, purchased by the first  Earl of Leicester and still at Holkham Hall, in which Barret has reversed the image in his painting.
There are a number of other Italianate paintings showing ruins which Barret probably painted before developing his series of Irish landscapes.
Barret's first major patron was probably  Joseph Leeson, 1st Earl of Milltown, who built the Palladian mansion,  Russborough House in the southern part of County Wicklow.
Richard Cassels was the architect and the house was furnished by Joseph Leeson, who travelled on grand tours of Europe in 1744 and again i n1750, amassing a large art collection of paintings, sculpture, furniture, and antiques.
This was augmented by classical landscapes and local landscapes.
Barret's paintings were used as a decorative scheme in the newly created dining room Many of Barret's paintings passed with the Milltown bequest to the National Gallery of Ireland in 1902.

Another source that was used extensively by Barret were engravings by Piranesi which were published in 1748 in Antichita romane de' tempi della Repubblica, e de' primi imperatori.
 A landscape commissioned by Lord Bective for Headfort, Kells, Co. Meath is based on the Tempietto del Clitunno a temple on the river Clitunnonear Spoleto, in central Umbria, north of Rome.
Early in his career Barret produced many oil paintings of classical scenery, often incorporating mythological figures. There is no evidence that Barret ever travelled to Italy and his name does not appear in John Ingamells listing of British Travellers to Italy. Most, if not all, of these paintings appear to have been commissioned for houses in Ireland and Barret does not seem to have painted Italianate paintings after he left Ireland. Thomas Bodkin considered that the oil paintings of Tivoli in Italy which had been attributed to him, to be more likely to be work of his son George Barret junior. who also produced many paintings with classical themes. However, these paintings can now be securely attributed to the elder Barret.  
A source of Barret's earliest landscape paintings came from the re-working of engravings of classical Italianate scenes of artists such as Claude Lorrain. A pair of paintings sold in 2013, came from the collection of the Rev. Samuel Madden (1686–1765). Madden established a series of prizes at Trinity College, Dublin, to reward agricultural and artistic enterprise, designed an important landscape garden on the shores of Lough Erne, founded the Dublin (later Royal) Society, and left an important collection of 17th- and 18th-century Italian pictures to Trinity College. These two paintings were based on engravings of two paintings by  Claude Lorrain. One of these is after Landscape with a rural dance, which belonged to the Duke of Kingston. The second is a Landscape with Argus guarding Io, purchased by the first  Earl of Leicester and still at Holkham Hall, in which Barret has reversed the image in his painting. There are a number of other Italianate paintings showing ruins which Barret probably painted before developing his series of Irish landscapes. Barret's first major patron was probably  Joseph Leeson, 1st Earl of Milltown, who built the Palladian mansion,  Russborough House in the southern part of County Wicklow.Richard Cassels was the architect and the house was furnished by Joseph Leeson, who travelled on grand tours of Europe in 1744 and again i n1750, amassing a large art collection of paintings, sculpture, furniture, and antiques. This was augmented by classical landscapes and local landscapes. Barret's paintings were used as a decorative scheme in the newly created dining room Many of Barret's paintings passed with the Milltown bequest to the National Gallery of Ireland in 1902.
Another source that was used extensively by Barret were engravings by Piranesi which were published in 1748 in Antichita romane de' tempi della Repubblica, e de' primi imperatori.  A landscape commissioned by Lord Bective for Headfort, Kells, Co. Meath is based on the Tempietto del Clitunno a temple on the river Clitunnonear Spoleto, in central Umbria, north of Rome.
George Barret Sr.