| Oasis Centre des femmes | Toronto |
| Of Rack and Room | Central Huron |
| Office of the Fire Marshal, Gravenhurst, Public Safety Training Division - Ontario Fire College Resource Centre | Gravenhurst |
| Ombudsman for Banking Services and Investments, Toronto | Toronto Downtown |
| Ombudsman Ontario | Toronto |
| On Stage Dance Studio | Stratford |
| ONE CARE Home & Community Support Services, Dining for Seniors - Stratford, Stratford | Stratford |
| ONE CARE Home & Community Support Services, EasyRide Transportation, Stratford | Stratford |
| ONE CARE Home & Community Support Services, Home Help, Stratford | Stratford |
| ONE CARE Home & Community Support Services, Mailing Address Only, Seniors' Centre Without Walls | Central Huron |
| ONE CARE Home & Community Support Services, Meals on Wheels, Stratford | Stratford |
| ONE CARE Home & Community Support Services, Reassurance Services, Stratford | Stratford |
| ONE CARE Home & Community Support Services, Stratford, Home At Last | Stratford |
| ONE CARE Home & Community Support Services, Stratford, ONE CARE Home & Community Support Services, Stratford | Stratford |
| ONE CARE Home & Community Support Services, Various Locations, Exercise & Wellness Programs | Central Huron |
| Ontario Association of Optometrists, Eye See...Eye Learn | Toronto Downtown Central |
| Ontario Camps Association | Toronto |
| Ontario Canola Growers' Association | Grey Highlands |
| Ontario Civilian Police Commission | Toronto |
| Ontario College Application Service | Guelph |
| Ontario College of Trades | Toronto Downtown |
| Ontario Dental Association | Toronto Downtown North |
| Ontario Energy Board (Central East) | Toronto |
| Ontario Energy Board (Central East), Central East Ontario - No Physical Address, Low-Income Energy Assistance Program (LEAP) - Central East Application Sites | Toronto |
| Ontario Federation for Cerebral Palsy | Etobicoke North |
| Ontario Federation of Teaching Parents | Ontario |
| Ontario Fencing Association | Toronto |
| Ontario Health - Trillium Gift of Life Network | Toronto Downtown Central |
| Ontario Health atHome South West Area, Stratford Office, Care Coordination, Stratford Office | Stratford |
| Ontario Health atHome South West Area, Stratford Office, Information and Referral | Stratford |
| Ontario Health atHome South West Area, Stratford Office, In-Home Services | Stratford |
| Ontario Health atHome South West Area, Stratford Office, Ontario Health atHome | Stratford |
| Ontario Health atHome South West Area, Stratford Office, School Health Support Services | Stratford |
| Ontario Home Health | Stratford |
| Ontario Human Rights Commission, 180 Dundas St W | Toronto Downtown |
| Ontario Motor Vehicle Industry Council | Toronto |
| Ontario Nature | Toronto Downtown |
| Ontario Parole Board, Victim Support | Toronto |
| Ontario Photo Card | Ontario |
| Ontario Poison Centre | Toronto Downtown Central |
| Ontario Provincial Police, Orillia - Memorial, General Headquarters | Orillia |
| Ontario Provincial Police, Sebringville, Perth County Detachment | Perth East |
| Ontario Universities' Application Centre | Guelph |
| Ontario Woodlot Association, Huron Perth Chapter | Stratford |
| Ontario. Members of Provincial Parliament (Perth Wellington), Perth Wellington Riding, Provincial Constituency Office - Matthew Rae - Perth-Wellington Riding | Stratford |
| Ontario. Ministry for Seniors and Accessibility | Toronto |
| Ontario. Ministry of Advanced Education and Skills Development, Employment Ontario Hotline | Toronto Downtown |
| Ontario. Ministry of Agriculture, Food and Agribusiness, Clinton, Clinton Resource Centre | Central Huron |
| Ontario. Ministry of Agriculture, Food and Agribusiness, Stratford - Lorne Ave E, Stratford Resource Centre | Stratford |
| Ontario. Ministry of Children, Community and Social Services, Mailing address, ServiceOntario INFOline | |
| Ontario. Ministry of Children, Community and Social Services, Ontario Autism Program | Toronto |
| Ontario. Ministry of Children, Community and Social Services, Post Adoption Disclosure Unit | Toronto |
| Ontario. Ministry of Children, Community and Social Services. Family Responsibility Office | Toronto |
| Ontario. Ministry of Children, Community and Social Services. Support Services for Male Survivors of Sexual Abuse Program | Toronto |
| Ontario. Ministry of Children, Community and Social Services. Victim Support Line | Toronto |
| Ontario. Ministry of Children, Community and Social Youth Services, Stratford, Youth Justice Services, Stratford | Stratford |
| Ontario. Ministry of Community and Social Services, Accessibility for Ontarians with Disabilities Act, Online/Web Service | Ontario |
| Ontario. Ministry of Economic Development, Trade and Employment/Ministry of Research and Innovation, 56 Wellesley St. W, Entrepeneur Branch Summer Company Program | Toronto Downtown |
| Ontario. Ministry of Education, Central East Region, Child Care Quality Assurance and Licensing | Toronto |
| Ontario. Ministry of Environment, Conservation and Parks, Peterborough - Mailing Address, Natural Resources Information and Support Centre | Peterborough |
| Ontario. Ministry of Environment, Conservation and Parks, Pinery Provincial Park, Ontario Parks - Pinery Provincial Park | Lambton Shores |
| Ontario. Ministry of Finance., Oshawa, Retail Sales Tax | Oshawa |
| Ontario. Ministry of Government and Consumer Services. Consumer Protection Ontario | Toronto |
| Ontario. Ministry of Health, Public Health Care | Toronto Downtown Central |
| Ontario. Ministry of Health, Trillium Drug Program | Etobicoke |
| Ontario. Ministry of Health, Health Care Connect | Toronto Downtown Central |
| Ontario. Ministry of Health, Health811 | Toronto Downtown Central |
| Ontario. Ministry of Health, Ontario's Fertility Program | Toronto Downtown Central |
| Ontario. Ministry of Health, Sexual Health Infoline Ontario | Toronto Downtown |
| Ontario. Ministry of Health, Smoking Cessation Program | Toronto Downtown Central |
| Ontario. Ministry of Health, Assistive Devices Program | North York Central |
| Ontario. Ministry of Health, Home Oxygen Therapy | North York Central |
| Ontario. Ministry of Health, Ontario Public Drug Programs | Etobicoke |
| Ontario. Ministry of Health, Ontario Health Insurance Plan | Toronto Downtown Central |
| Ontario. Ministry of Health, Dental Care For Low-Income Seniors | Toronto |
| Ontario. Ministry of Labour, Immigration, Training and Skills Development. Employment Practices Branch | Toronto |
| Ontario. Ministry of Long-Term Care, Long-Term Care Family Support and Action Line | Toronto Downtown Central |
| Ontario. Ministry of Long-Term Care, Reports on Long-Term Care Homes | Toronto Downtown Central |
| Ontario. Ministry of Municipal Affairs and Housing. Rental Housing Enforcement Unit | Toronto |
| Ontario. Ministry of Northern Development, Mines, Natural Resources and Forestry, Southern Region - Peterborough | Peterborough |
| Ontario. Ministry of the Attorney General, Enforcement Offices, Stratford - 100 St Patrick St | Stratford |
| Ontario. Ministry of the Attorney General, Ontario Court of Justice - Criminal Court Operations, Stratford - 100 St Patrick St | Stratford |
| Ontario. Ministry of the Attorney General, Ontario Court of Justice - Family Court, Stratford - 100 St Patrick St | Stratford |
| Ontario. Ministry of the Attorney General, Stratford - 1 Huron St., Superior Court of Justice - Civil Court | Stratford |
| Ontario. Ministry of the Attorney General, Stratford - 1 Huron St., Superior Court of Justice - Family Matters | Stratford |
| Ontario. Ministry of the Attorney General, Stratford - 100 St Patrick St, Family Law Information Centre | Stratford |
| Ontario. Ministry of the Attorney General, Stratford - 100 St Patrick St, Ontario Court of Justice, Stratford - St. Patrick St | Stratford |
| Ontario. Ministry of the Attorney General, Stratford - 75 Waterloo St S, Victim / Witness Assistance Program | Stratford |
| Ontario. Ministry of the Attorney General, Superior Court of Justice - Criminal Court, Stratford, Stratford - 1 Huron St. | Stratford |
| Ontario. Ministry of the Attorney General, Superior Court of Justice - Small Claims Court, Stratford - 100 St Patrick St | Stratford |
| Ontario. Ministry of the Attorney General, Toronto, Office for Victims of Crime | Toronto Downtown |
| Ontario. Ministry of the Attorney General. Justice Ontario, Toronto | Toronto |
| Ontario. Ministry of the Attorney General. Office of the Children's Lawyer | Toronto |
| Ontario. Ministry of the Attorney General. Office of the Public Guardian and Trustee | Toronto |
| Ontario. Ministry of the Attorney General. Public Guardian and Trustee, Capacity Assessment Office | Toronto Downtown |
| Ontario. Ministry of the Solicitor General, Stratford - St Andrew St - Stratford Jail, Stratford Jail | Stratford |
| Ontario. Ministry of the Solicitor General, Stratford, Probation and Parole Services | Stratford |
| Ontario. Office of the Worker Adviser, Scarborough Office, Ontario. Office of the Worker Adviser, Scarborough Office | Toronto |
| OPAL Self-help for Physically Challenged | West Perth |
| Operation Organize, Mailing Address, Solutions for Seniors | Perth East |
| Optimism Place Women's Shelter and Support Services, Counselling and Transition Supports, Stratford | Stratford |
| Optimism Place Women's Shelter and Support Services, Family Court Support Program, Stratford | Stratford |
| Optimism Place Women's Shelter and Support Services, Listowel, North Perth Resource Centre | North Perth |
| Optimism Place Women's Shelter and Support Services | Stratford |
| Optimism Place Women's Shelter and Support Services, Child and Youth Services | Stratford |
| Optimist Club of Ellice, Club 46069 Zone 1 | Rostock |
| Optimist Club of Mitchell, Club 46136 Zone 1 | Mitchell |
| Optimist Club of Mornington, Club 46145 Zone 1 | Milverton |
| Optimist Club of Stratford, Stratford Legion, Club 46220 Zone 1 | Stratford |
| Optimist International, Seaforth & District, Optimist Club - Club 46923 Zone 2 | Seaforth |
| Optimist International, St Pauls, Optimist Club of Downie - Club 46051 Zone 1 | St Pauls |
| Optimist International, Shakespeare, Optimist Club 46203 Zone 1 | Shakespeare |
| Order of The Eastern Star, St Marys - Mailing Address, Order of the Eastern Star - Chapter 121 | St Marys |
| Ovarian Cancer Canada | Toronto Downtown |