| Last | First | Middle | Suffix | Desig | Company | City | State / Province |
Country |
| Oberlander | Cornelia | A. | FASLA, CSLA | C H O Landscape Architect | Vancouver | BC | Canada | |
| O'Boyle | Robert | L. | FASLA | O'Boyle Cowell Blalock | Hickory Corners | MI | ||
| Ochis | Gregory | ASLA | Design Workshop | Denver | CO | |||
| O'Donnell | Nancy | Q. | ASLA | The Pennsylvania Horticultural Society | Philadelphia | PA | ||
| O'Donnell | Patricia | M. | FASLA | LANDSCAPES - LA Planning Historic Preservation | Charlotte | VT | ||
| O'Hara | David | CSLA | City of Toronto | Toronto | ON | Canada | ||
| Okamura | Steve | ASLA | Port of Seattle | Seattle | WA | |||
| O'Leary | Jennifer | ASLA | Wheat Scharf Associates | Tucson | AZ | |||
| O'Leary | Patrick | J. | ASLA | HGOR Inc | Atlanta | GA | ||
| Olinger | Edward | J. | FASLA | Rochester | NY | |||
| Olinger | Judy | F. | ASLA | Judy Olinger Inc | Huntingburg | IN | ||
| Olivo | John | A. | B W Bosenberg & Company Inc | Far Hills | NJ | |||
| Olsen | Christopher | SUNY College of Environmental Science & Forestry | Syracuse | NY | ||||
| Orland | Brian | Penn State University | University Park | PA | ||||
| O'Rourke | Mark | Shearon Environmental Design Co | Plymouth Meeting | PA | ||||
| Orr | Howard | R. | Jr. | ASLA | Cumming | GA | ||
| O'Shea | James | E. | ASLA | Parks & Recreation KCMO | Kansas City | MO | ||
| Ostrowski | George | A. | Jr. | ASLA | Land Design Studio | Royal Oak | MI | |
| Otsuji | Dennis | Y. | FASLA | ONA Inc | San Diego | CA | ||
| Owens | Peter | Marshall | The Presidio Trust | San Francisco | CA | |||