Spokeswoman Taiva Tegler says 10 students occupied the office for about two hours before they were removed by Ottawa police.
She says eight have been charged with trespassing.
Tegler says the students staged the protest on the eve of the Ontario budget to demand the Liberal government follow through on its election promise to reduce tuition.
Earlier this month, the government announced that its cap on tuition fee increases will remain at five per cent, which has been the case since 2006.
The students also want the budget to include the extension of the Ontario Student Assistance Program to part-time students and the hiring of more professors.
"Their message, I think, is pretty loud and clear that when students are left in a desperate situation they're going to continue to fight back," Tegler said.