In the afternoon of the following Monday, May 20, a large group of BSU members and their supporters entered Odegaard’s office suite at approximately 5:20pm. They expected to find Odegaard and Gov. Evans there, and they intended to keep the men in the office until their demands were met. Instead the BSU members found that they had interrupted a Faculty Senate Executive Committee meeting and Evans was not present. Several protesters entered the meeting room and sat on the floor while others secured the suite. The subject of the meeting immediately changed to the BSU's demands and continued with hostile exchanges. By 6:40pm the discussion had stopped, Odegaard and most of the other administrators withdrew into the inner office and were barricaded in by protesters. This left the protesters in the outer-office, along with a few faculty members from the meeting who decided to stay and help the protest. The most prominent of these faculty members was Professor Arval Morris.
By 7 pm, the number of sit-in participants had grown to 150. Most of the students involved were young African-Americans, but some non-Blacks (such as Robbie Stern) were also involved. In spite of the efforts of the University’s Police Department to cut off the activists, protesters and supplies (such as groceries and a record player) were lifted up to the third story office by ropes outside the building. By 7:30pm the Seattle Police had arrived on the scene and helped UW police seal off the building.
At 8:15 p.m., Vice-President Donald K. Anderson and UW Police Chief Ed Kanz tried to deliver an ultimatum to the protesters: telling them to either leave on their own by 8.30pm or they would be removed by force. But this exchange was hampered by the heavy office doors that separated the protesters and the police. Around this time Michael Rosen, an American Civil Liberties Union lawyer who had helped Miller, Dixon, and Gossett in their case following the Franklin protest, arrived on the scene and began to establish negotiations. With the help of Rosen and the sympathetic faculty members, Brisker, Dixon and the BSU drafted a proposal that would meet their objectives. The proposal was delivered to Odegaard, negotiations continued, and at 8.45pm Brisker announced that Odegaard had signed the BSU proposal and the sit-in was over. The protesters left Odegaard’s office chanting “Beep-beep, bang-bang, ungawa, Black Power!”