Ngongotaha is the only exception and will have local club Central Lions playing as their reserve team in 2015.
A division one grade has also been created, including eight teams: Papamoa, Tauranga, Te Puke, Reporoa, Tauhara, Mangakino, Putaruru and Forestland (Tokoroa).
An under-15 and under-17 competition will also be in place combining both districts, while the under-13 and under-14 age group will remain the same.
Upper Central Zone Rugby League general manager Sash Stosic said it was a great result for the two league districts.
"I think the Coastline and Bay of Plenty clubs will be in a very strong position next year. There is a guaranteed strong competition for their youth and senior teams," he said.
"They will have one of the largest club competitions in the country outside of Auckland."
Stosic said the two districts shared a strong focus on youth and growing the game.
"We are very excited, I think for the first time that I have been here Coastline and Bay of Plenty are on the same page."
Stosic said they had also been working with Waikato clubs to create an even wider competition, but Waikato had decided not to come on board.
"Waikato are going to carry on and do their own thing for 2015."
He said getting the age group grades to match up and also the travel were two major barriers for Waikato clubs.
However, he said they would revisit that option at the end of next season.
The Bay of Plenty District covers a huge area including Rotorua, Taupo, Turangi, Tokoroa, Mangakino and Putaruru. Coastline covers the area of Tauranga, Whakatane and Kawerau.
Local coach Doug Unuwai, who led Pikiao to the 2014 Bay of Plenty premier title this season, said it was a great move for rugby league in the area.
"It is something we have been looking forward to for the last couple of years."
The last time a similar competition was held was 2012 when the Waikato/Bay of Plenty/Coastline competition was still functioning.
The 2015 season will run from April to August.
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Model for senior clubs in 2015:
Premier grade: Pikiao, Ngongotaha, Pacific (Tokoroa), Taupo, Otumoetai and Putauaki (Kawerau)
Reserve division: Pikiao, Central, Pacific, Taupo, Otumoetai and Putauaki
Division one: Papamoa, Tauranga, Te Puke, Reporoa, Tauhara, Mangakino, Putaruru, and Forestland (Tokoroa).