The museum site is located on the eastern promontory of the Osage Hills and displays native oaks, hickory and ash trees as well as species of flowering trees and evergreens that the original owner, Mr. Thomas Gilcrease, introduced to the site. Besides the museum, which has expanded to 127,000 square feet, the site harbors a small mausoleum, parking area, and driveways. The site has an excellent view of the city skyline to the southeast and a beautiful view of the Osage Hills to the west. Natural features of the 125-acre site include an extensive north facing rock escarpment, a deep rugged ravine, three ponds, wooded areas and creeks. There is an abundance of wild flowers and a variety of bird species, deer and small woodland animals. These attributes are to be preserved and utilized in a Master Plan foreseeing greatly increased visitation to the museum.

The grounds were to be brought up to the high standards of the museum through the use of appropriate theme gardens indicative of the periods of American culture represented in the museum collection. The owner determined that there would be gardens based on such eras as the museum collection expanded. We were asked to design two theme gardens encompassing the pre-Columbian, Pioneer, Colonial and Victorian eras. A picturesque garden, an American rock garden, and an outdoor sitting area dedicated to the Gillies, the museum volunteer corps, have been incorporated into the Master Plan. The slopes, topography, drainage, vegetation and views were analyzed with the prospect of providing parking for 100 additional cars without reducing the environmental quality of the grounds. Parking lots were planned for the north and south sides of the entrance. Linking the lots to the entry is a gently curving pedestrian spine reinforced by a colonnade of Shumard oaks. The grounds committee originally selected an area east of the museum for all of the theme gardens, but due to the scale of the gardens and the need to view them as separate entities, we dispersed the theme gardens, screening each one from the other.

The gardens are either located along the main pedestrian spine or on trails derived from the main spine and are fully accessible to the disabled. Evergreens are used throughout the grounds to screen undesirable off site views. Masses of azaleas, whose blooming time corresponds with the annual Gilcrease outdoor festival, have been planted throughout the site.

The site was transformed into a regional showplace that has taken center stage for such events as the U.S. Open Golf Tournament, the National Governors Conference, and major museum exhibits.