Property developer Bernard Duffy has been refused permission to build 342 Co Galway homes on former golf course lands owned by the Comer Group.
An Bord Pleanála ruled that Alber Homes' plans for Rosshill Manor had flaws and could harm wildlife in nearby Galway Bay.
Rosshill Manor would have mixed 185 houses of two to four bedrooms with 157 apartments in five four-storey blocks and one three-storey block. Alber had sought fast-track approval to develop the 10-hectare (25 acre) site via strategic housing rules.
But the plans attracted more than 40 objections, including from owners of some of the half-dozen nearby farms. One said dairy cattle were driven daily across the road beside the proposed development.
Others, including An Taisce, said the rural area had too little public transport to cope with more than 1,000 new residents.
The planning board refused permission citing environmental, sewage and design issues.
Its ruling, signed by architect and board member Michelle Fagan, said Rosshill Manor had "poorly defined and poorly overlooked streets and open spaces, a high number of cul-de-sacs, and a lack of variety and distinctiveness in the design of the dwellings".
The proposed development, it said, "fails to integrate existing trees and woodlands satisfactorily".
It said such faults would result in "a substandard form of development and would be seriously injurious to the residential amenities of future occupants".
An Bord Pleanála said it "cannot be satisfied beyond reasonable scientific doubt" that the proposed housing would not harm wildlife in the Inner Galway Bay Special Protection Area, in part because the board had received no "seasonal bird surveys for the site".
It said "existing deficiencies in the wastewater network" would face heavy demand from hundreds of new residential dwellings.
Glenamaddy-born brothers Luke and Brian Comer purchased the former par-3 golf course in Rosshill for a reported €3m in 2013.
In January, Mr Duffy's Alber Homes sought direct approval from An Bord Pleanála under fast-track rules that allow residential developments of at least 100 units to bypass consideration by local councils. Alber had included a two-storey crèche and playground in its proposal.
Recent projects by Galway-based Alber include The Nurseries, 31 homes on Taney Road in the Dublin suburb of Dundrum; Castlebrook Manor, 82 homes on Walker's Road in Limerick; and Léana Theas, 24 homes on Cappagh Road, Galway.