In 1899 the Nationaltheatret, which was to present both theatre and opera, was opened. For this the orchestra expanded to 44 musicians, and was conducted by Johan Halvorsen. The orchestra served the Nationaltheatret in two roles: providing music for the new theatre and performing symphony concerts for the Music Society.
During the First World War, the desire for symphonic music grew, along with inflation, leading to a dispute between the orchestra and the Nationaltheatret and a temporary collapse of the Musikerforening's concerts. Thus, in 1919, the orchestra was reformed as the Filharmonisk Selskaps Orkester (Orchestra of the Philharmonic Company) by private shareholders and initiative. The first season was shared by three conductors; Johan Halvorsen, Georg Schnéevoigt and Ignaz Neumark.
Filharmonisk Selskaps Orkester's first concert took place in Logen on 27 September 1919, with 59 musicians on stage and with Georg Schnéevoigt as conductor. On the repertoire was Rikard Nordraak's 'Ja, vi elsker dette landet', Johan Svendsen's 'Fest polonaise', Christian Sinding's 'Symphony No. 1', Edvard Grieg's 'Piano Concerto in A minor', and finally 'Landkjenning', with the singer Erik Ole Bye as baritone soloist.
Among the guest musicians of this first season were the conductor Arthur Nikisch, the pianists Eugen d'Albert, Edwin Fischer, Wilhelm Kempff, Ignaz Friedman and Artur Schnabel and the violinists Bronislaw Huberman and Carl Flesch. Between September 1919 and May 1920, the orchestra gave 135 public concerts, most of them sell-outs.
The first Norwegian radio broadcast started in April 1923, and shortly after, the first radio concert with the Oslo Philharmonic Orchestra. From 1925, there was a contract between the orchestra and the Norwegian Broadcasting Corporation (NRK), ensuring weekly live broadcast concerts. This contract with NRK saved the orchestra from bankruptcy in the 1930s. Issay Dobrowen joined the orchestra in 1927; when he left in 1931, the position of chief conductor was divided between two Norwegians: Odd Grüner Hegge and Olav Kielland. After 1933, Kielland became sole chief conductor until 1945.
In 1953 Oslo hosted the ISCM Festival, which brought further international contacts in the awareness of new repertoire, which many of the Scandinavian countries had been deprived of during the years of World War I and World War II. The first performance of the Oslo Philharmonic outside Scandinavia took place in 1962. Since then, the orchestra has much international acclaim.
In 1979, the orchestra formally changed its name to Oslo Philharmonic Orchestra. In 1996, an act of the Norwegian parliament made the orchestra an independent foundation. Although the orchestra has maintained high standards of quality since its inception and under various renowned musical directors, many consider that it saw its largest leap forward during the tenure of Mariss Jansons from 1979 to 2002. During this time the orchestra recorded readings of Tchaikovsky's symphonies, and went on international tours. The Oslo Philharmonic won international acclaim with its Tchaikovsky cycle and a very successful series of recordings for EMI. In 2000 the orchestra completed a cycle of Bartók for Simax. Other awards won by the Oslo Philharmonic include Grand Prix du Disque, Diapason d'Or, and the German Classical Music Award.
Subsequent music directors have been André Previn (2002-2006) and Jukka-Pekka Saraste (2006-2013). Saraste now has the title of æresdirigent (conductor laureate) with the orchestra. In February 2011, the orchestra announced the appointment of Petrenko as its next chief conductor, as of the 2013-2014 season, with an initial contract of 4 years.