The Big Ten added Oregon and Washington as new members Friday, strengthening the Western flank of the rapidly growing conference while dealing a major blow to the Pac-12.

The league's presidents and chancellors unanimously voted to add the schools, which, along with USC and UCLA, will officially join the Big Ten on Aug. 2, 2024. The Big Ten, which has expanded four times since 2010 after adding no schools the previous 21 years, is set to become the largest major athletic conference at 18 members.

"We are excited to welcome the University of Oregon and the University of Washington to the Big Ten Conference," Big Ten commissioner Tony Petitti said in a statement. "We look forward to building long-lasting relationships with the universities, administrators and staff, student-athletes, coaches and fans. Both institutions feature a combination of academic and athletic excellence that will prove a great fit for our future."

Unlike USC and UCLA, Oregon and Washington will not enter the Big Ten with full revenue shares. Sources told ESPN that both schools will receive approximately $30 million annually when they join the league, a share that will increase by $1 million during the current media contract with Fox, NBC and CBS, which runs through the 2029-30 athletic season. They then would be able to receive full shares. The other Big Ten members are expected to receive more than $60 million annually from the new agreement this year, an amount that will increase over the life of the deal. Previous Big Ten expansion additions Nebraska, Rutgers and Maryland also did not receive full revenue shares immediately.

Factoring in other media revenue streams over a 10-year period, Oregon president Karl Scholz said, "We anticipate averaging over $50 million just from direct media rights."

After a longer and secretive process to add USC and UCLA in June 2022, the Big Ten moved quickly on Oregon and Washington. The league had been focused on integrating USC and UCLA but mobilized after the Pac-12 lost Colorado to the Big 12 and could not gain enough traction for its streaming-heavy media rights deal, presented to presidents and chancellors on Tuesday morning. A sub-group of four Big Ten presidents and chancellors began exploring expansion possibilities Wednesday, focusing on Oregon, Washington, Cal and Stanford before refining their focus to the two Northwest schools.

"When considering the full spectrum of academic, athletic and research excellence, the alignment with our member institutions is extremely clear," Illinois chancellor Robert Jones, chair of the Big Ten council of presidents/chancellors, said in a statement. "We are excited to welcome them and look forward to collaborating and competing with them in the years ahead."

Despite some initial reluctance from members about the speed of the expansion push and the potential damage to the Pac-12, a historic partner in the Rose Bowl Game and other ventures, Big Ten leaders accelerated their efforts in the past day to land Oregon and Washington, according to sources. None of the departing Pac-12 schools will have to pay an exit fee to depart the league because of an expiring media rights deal in 2024.

The Big Ten had examined both Oregon and Washington as expansion candidates last fall, in the wake of the USC and UCLA additions, but then-commissioner Kevin Warren could not rally enough support among presidents and chancellors to approve them. Petitti, hired in April, told ESPN last week that he wasn't focused on additional expansion beyond USC and UCLA but added: "There's a flow of information, keeping people updated on what's going on, how we see the landscape, trying to help predict what we think will be next."

"We have tremendous respect and gratitude for the Pac-12, its treasured history and traditions. At the same time, the college athletics landscape has changed dramatically in recent years," Washington athletic director Jennifer Cohen said in a statement. "The Big Ten's history of athletic and academic success and long-term stability best positions our teams for future success, and we are energized at the opportunity to compete at the highest level against some of the best programs in the country."

The expansion additions mean the Big Ten will reissue its 2024 and 2025 football schedules, announced in early June. Sources say the league is expected to maintain the key elements of the "Flex Protect Plus" model, which set 11 annual matchups between rivals but increased the overall rotation of games, while eliminating divisions. The Big Ten based the model on overall flexibility in its nine-game league schedule, varying the number of protected games per team.

"Accepting membership into the Big Ten Conference is a transformational opportunity for the University of Oregon to change the short and long-term trajectory of our university and athletics department," longtime Oregon athletic director Rob Mullens said in a statement. "The stability and exposure of joining the Big Ten is of great benefit to the University of Oregon."

Oregon and Washington give the Big Ten a more robust West Coast presence and potential travel partners for USC and UCLA. Although USC is the most decorated Pac-12 program set to enter the Big Ten, Oregon and Washington are the only Pac-12 teams to have appeared in the College Football Playoff. The Big Ten has had only one team, Ohio State, win or play for a national championship during the CFP or BCS eras.

It's unclear how Oregon and Washington's moves will impact their in-state rivalries with Oregon State and Washington State, though both schools indicated they would like to keep those rivalries alive.

When asked if Oregon would commit to playing home-and-home football series with Oregon State into perpetuity, Oregon AD Rob Mullens said, "Our goal would be to schedule Oregon State in every sport that's possible. Football scheduling can be complicated because of how far out it is and the difficulty of playing nonconference games later in the year. But our goal would be absolutely to continue to play Oregon State."

Washington president Ana Mari Cauce said that the Huskies hope to continue Washington State across all sports.

"Even with this move, we remain committed to the Apple Cup and to competing with WSU across all of our sports," Cauce said.