The areas of Brunswick Park and Osidge are often considered to be a part of New Southgate or Southgate, but are traditionally within East Barnet and the old county of Hertfordshire. Osidge was originally a medieval name being used in the 12th century as 'Huzeheg'. The 'idge' part refers to a hedge and the Os could Hugh's Hedge or some other person's name. It may have been a hedge that was used as a boundary for Enfield Chase.
Brunswick Park is a much later name, which did not come into use until the second half of the 19th century. It was a popular place name with the Victorians because of its royal connections, and was possibly chosen after Frederick William Brunswick, a hero of the Battle of Quatre Bras (1815), or after Caroline of Brunswick-Wolfenbüttel, the second wife of George IV.
Until the railway was built the land was mostly farmland. In the late 1840s a railway line was built by the Great Northern Railway Company. It was this company who opened the Great Northern Cemetery (now New Southgate Cemetery) in 1861. Until the 1870s it had its own 'mortuary station', so that the dead could be brought from King's Cross by train. At its largest the cemetery occupied 80 acres of land. The most famous person buried there is Shoghi Effendi, a leader in the Bahai religion.
From the 1880s the area began to develop a small number of streets, particularly around the Brunswick Park Estate. In 1898 the North View Photographic and Stereoscopic Works was opened, the first industrial manufacturing in the area. This was joined in 1922 by a large electronics company called Standard Telephone and Cables (STC).
STC employed nearly 10,000 people at the height of its production. During World War Two the factory was hit by a German V1 rocket and 33 people were killed. Today the site is occupied by North London Business Park, and is occupied by the London Borough of Barnet.
The largest house in this part of East Barnet is Osidge House. In 1893 the house was bought by Thomas Lipton. Lipton was famous selling tea and racing boats. Later the house became the Sir Thomas Lipton Memorial Hostel for elderly women.