Rebengiuc's first drama role was as Biff in Arthur Miller's play "Death of a Salesman", a performance which he regrets, describing its director, Dinu Negreanu, as an untalented person promoted over "political reasons". He also recounts that training for the part brought his first collaboration with Liviu Ciulei, which he sees as one of the few positive aspects of the production. At around the same time, he began a collaboration with the "Teatrul Mic" company and director Radu Penciulescu, being, together with Leopoldina Bălănuţă, George Constantin and Olga Tudorache, one of the first actors to embark on the project. Rebengiuc appeared in several of Penciulescu's experimental productions: "Two for the Seesaw" by William Gibson, "Tango" by Sławomir Mrożek and "Richard II" by William Shakespeare. Theater critic Simona Chiţan saw the collaboration as an aspect of the liberalization following the socialist realist years: "Penciulescu and Rebengiuc have thus opened [...] a positive period for Romanian theater: the repertoire had been widened, foreign, not just Soviet, plays were being performed, authors modern for the age in question had their plays produced."