In 1934 some members including Dr. O'Kelly, J.B. Stronge, G.A. Claffey; Michael and Joe O Keeffe, approached by George Munro, agent for the Harewood estate (previously Clanricardes) with a view to locationg to locationg a golf course on the estate, Mr Munro put the proposal to the Earl of Harewood. He replied on the 20th of December 1934 that he would have no objection to giving the land for a Golf course provided that if at any date in the future that he required the land in connection with a stud farm, the Club would have no grievance if he took the land back from them. The terms of letting were that the club were to have the lands free of rent for the first year, a rent of £15 for the second year and £20 per year thereafter. The Golf Club merely had playing rights over the land and the Harewood Estate reserved the right to graze the lands. Therefore, it was necessary to fence the greens. The new course was laid down by MF O'Keeffe, B.E. and was opened by Monsignor Joyce on the 30th June 1935.In that year also a new pavilion was constructed by the Molloy brothers, Danny and Fergus who owned sawmills in the town. The timber was supplied by Mr McGuinness of McAinsh & Co. free of charge.
A number of ladies had already taken up the game while the Claggernagh course was in use. These included Miss Lally( later Mrs Mitchell), Miss Connolly, Miss O' Leary,s Taylor, Mrs O'Kelly and Maura Lynch (later Mrs Glynn). When the new course was opened, Monsignor approached Maura Glynn to put ladies golf on a firm footing and affiliate the ladies club to the I.L.G.U. She became more acquainted with the rules of the game with the assistance of Mrs Sweeney who was Secretary of Birr Golf Clubat the time. The lady golfers competed against the ladies of Birr, Ballinasloe, Roscrea, Gort, Loughrea and others. When visiting teams came to Portumna the ladies did the catering, hired out the cutlery for 1s from Mrs Keary of Keary's Hotel, and later from Mrs Burns of the Hydro Hotel in Abbey Street(now owned by the Shiel family).
The Forestry Commission purchased the Harewood Estate in 1947 and acquired it subject to the Golf Club's tenancy. It generously gave the Golf Club exclusive rights over the land of the course. This meant it was no longer necessary the fence the greens and the Golf club had the grazing rights of the course which they let for a short time for sheep grazing. During these years the club was renting the land on a yearly basis. When Michael Bermingham, a teacher in the Vocatioonal School, became Hon.Secretary in 1951, he negotiated a 99 year lease of the property from the Department of Lands. He was greatly assisted in this by Patrick Beegan, T.D., who was then Parliamentary Secretary to the Deparrtment of Finance. Previously long serving Hon. Secretary Mr David Frawley must be given credit for his work in this area. The course was completely altered in accordance with recommendations of Mr. Dan O'Brien, who had been the golf professional at Ennis Golf Club and had now been appointed to Portumna Golf Club.
In 1956, the clubhouse had been enlarged by the addition of a concrete building which included a modern toilet facilities and a bar. During Michael Bermingham's time as secretary, the club made marvellous strides in every way and, on his leaving portumna for Dublin he was made an honorary life member of the club. During the late 50s and early 60s the club fell upon lean times as the number of members gradually dwindled. Little development took place apart from the purcahase of a small tractor and a triple gangmower to replace the single horse drawn mower.
In 1963, the club held it's Golden Jubilee and a special Open Week was held during that year. The club also won the Galway County Trophy, a competition which they hosted in that year.
In the early 1970s things began to improve, thanks to the efforts of Eamon Lynch, Seamus Deely (a vet based in Portumna at the time), Michael J. Kelly and Daithi Frawley. In 1970 during the Captaincy of Seamus Deely, it was decided to build a completely new clubhouse as tourists were increasingly using the club and the old clubhouse was not adquate. With generous assistabce from Bord Failte the new modern clubhouse was erected and was opened in 1971 by Mr. Sean Flanagan, the then minister for Lands. On that occasion he announced that his department had decided to give the Club a lease on a further area of land for which it had applied so that the course could be extended to an 18 hole course.
The new course was completed with the aid of FÁS, the Training and Employment Authority, and Sean Ryan who acted as course manager. Without Sean Ryan's vision and drive the course would not have been developed at the speed and cost that it was. Eddie Connaughton, the course architect, was instructed by the club to draw up a design for a new 18 hole championship course. The key objective was to ensure that the 9th and 18th holes were as near as possible to the clubhouse.
The course was opened on Sunday June 21st 1992, by Liam Reidy, President of the Golfing Union of Ireland.
In 1993, during the captaincy of Frank Kilkenny, the club purchased the outright title of the existing course of 88 acres plus another 38 acres for further development, from Coillte for £90,000. Now, for the first time, the club owned it's own property.
With an expanding membership and an increasing number of visitors, the clubhouse facilities became grossly inadquate. The club began planning for the upgrading of the facilities, initially proposing a new build close to the 15th green. But after much discussion, it was decided to upgrade and expand the existing clubhouse.
Work on the new clubhouse as well as the 5th, 6th and 7th holes was concluded by 2000, and the official opening took place in September.
In 2003, Paddy Kelly became the new course manager, and oversaw the upgrading of the course, building two new greens on the 11th and 13th holes, and also a new practice putting green. Later this year, the club hosted a number of national competitions, including the Irish Club Youths, the Irish Schools Championship and the Boys Inter-provincial Championship, which was an endorsement for the the improvements that had been carried out on the course.
In 2005, the club hosted an Irish Youths International between Ireland and Scotland, which Ireland won, and which featured an up-and-coming future World No.1 in Rory McIlroy.
In 2008, new greens on the 2nd and 8th holes were completed, as well as the introduction of 50 mallard ducks to the island in the lake adjoining the 17th fairway.
To celebrate the club's 100 year existence in 2013, a centenary committee was formed in 2012 to prepare for the occasion. As part of the celebrations, the club hosted All Ireland Senior Close Championship, as well as the All Ireland Finals of the Ladies Senior Cup.