Olmsted Brothers’ work at Stoneleigh, which softened the Beaux Arts plan, was overseen by firm principal Percival Gallagher. The circular garden was retained but its interior fitted with an open lawn. The formal entry sequence was replaced by a curving drive, while pasturelands between the stable and Willow Cottage were converted into a paddock, and ultimately a great lawn. Careful manipulation of grading and planting ensured continuity between the earlier work and the new. The service aspects of the estate were subordinated while new house construction was accommodated through sensitive subdivision of the property. Beyond the house and gardens, curving walks and lawns afforded sweeping views from the preserved portions of the terrace. The Olmsted Brothers were brought back in for minor adjustments in 1937, to advise on selectively thinning overgrowth, and finally in 1958 following a severe winter storm.
In 1996 the property was placed under a conservation easement by the Haas’ son and daughter-in-law, and subsequently entrusted to Natural Lands in 2016 following their passing. Today the property is open to the public.