[1] Cerilli initially intended to run for the NDP in the centre Winnipeg riding of Broadway in the 1990 provincial election, but lost the party nomination to Conrad Santos by one vote.
She instead ran in the northeast Winnipeg riding of Radisson, where she defeated Progressive Conservative candidate Mike Thompson by almost 1500 votes (incumbent Liberal MLA Allan Patterson finished third).
The Progressive Conservatives won the general election again; during her time in opposition, Cerilli served as NDP critic for Housing, Workplace Safety, Health and Youth.
She was regarded as one of the more left-wing members of caucus, and was the only Manitoba MLA to support Svend Robinson, rather than Lorne Nystrom, for the leadership of the federal NDP in 1995.
The NDP were victorious in the 1999 provincial election, and Cerilli personally defeated Progressive Conservative Henry McDonald[4] by 5198 votes to 3114.