With 1995 marking the 20th anniversary of Himitsu Sentai Goranger, Toei had decided to make a serious anniversary series that harkened back to Sentai's beginning while taking advantage of the developments since then. For it's development, many writers from older series came back to work on the show with the plan for a dark theme. The five Ohranger themselves were to be similar to the Goranger in personality and former Goranger Hiroshi Miyauchi (who played AoRanger) was brought in as the mentor for the series. Yet, while initially keeping to this concept, the events that occurred in Japan during the show's production, such as the Subway Sarin Incident and the Kobe earthquake, forced the writers of Ohranger to constantly rewrite the script, resulting in the near cancellation of the Super Sentai series. The Ohrangers began to alternate between serious and lighter personalities, and many new weapons and toys were created to boost merchandising. While Ohranger ultimately had the lowest ratings of any Sentai series up to that time, the resulting toy sales were very strong and because of these heightened figures, the Sentai series ultimately began to focus on more gimmicks to continue these high merchandising figures.
600 million years ago, Pangaea created a robot named Bacchus Wrath, who ultimately turned on his creators. The KingRanger defeated Bacchus Wrath and banished him from Earth. In the year 1999, Bacchus returned to Earth as the ruler of the Machine Empire Baranoia with the intention of wiping out all human life and bring about machine rule. Chief Counsellor Miura revived super energies that had been born of the lost civilization of Pangaea with the intention of creating weapons to fight against Baranoia. The reassembling of a stone plate uncovered three years previously, the secrets of "Super Power" were revealed. Miura built a pyramid to generate Tetrahedron power in order to allow five U.A.O.H. officers to transform into Ohrangers.
"Oh" (オー,Ō) is a pun on "olé" (オーレ,ōre), "aura" (オーラ,ōra), and the Japanese word for "king" (王,ō). "O.H." was also given as the acronym for "Overtech Hardware", the organization the team is part of, adding to the pun.
This season, like it's successor season Carranger, would be notable for being anniversary series for the Super Sentai franchise and would pave the way for future anniversaries to come. For Ohranger in particular, it would be considered the 20th anniversary of the very first Sentai series, Himitsu Sentai Gorenger which, alongside its followup J.A.K.Q. Dengekitai, had become fully acknowledged as part of the Super Sentai franchise. Yet while it would attempt to depict itself as the 20th anniversary series, Ohranger's position as the 19th series would ultimately make the next true Sentai anniversary held off until 2001's Hyakujuu Sentai Gaoranger, which would be the 25th Sentai (though 26 years after Gorenger) and make every subsequent anniversary follow from every five series post-Gorenger, not every five years.
The events leading up to this series took place 600 million years earlier, marking the earliest point in the Sentai timeline so far.
Ohranger is considered to be the 3rd lowest rated Sentai show with a rating of 4.5% after Go-Busters with 4.0% and Kyoryuger with 3.9%. The explanation is the fact that it was meant to be a darker show (human terrorists attacking Japan) but the script had to be re-written because of the Tokyo Subway Attacks and the Great Hanshin Earthquake that put Ohranger into a mix-up between dark and comical episodes. Thus the ratings drastically decreased, leading to the almost-cancellation of the Sentai franchise.