Described by the German press as demonstrating “uncompromising honesty” (Neue Zeitschrift für Musik), praised for his unorthodox aesthetics (Hannoversche Allgemeine Zeitung), and whose work is called “brawny, high-contrast… full of rich counterpoint and compelling textural changes” (The New York Times), “strikingly individual” (The Toronto Star), and “wonderful-sounding” (The Buffalo News, Buffalo, USA) Grella-Mozejko has written on commissions from, among others, The Alberta Foundation for the Arts, The Canada Council for the Arts, Canadian Broadcasting Corporation, Canadian Polish Congress, Edmonton Arts Council/Clifford E Lee Fund, Ensemble MW2, International Conversatorium of Organ Music, Polish Ministry of Culture and Art, as well as Polish Radio, Canadian Music Centre, and The Flanders Festival.

In 1997, he won the Alberta Motion Picture Industries Association (AMPIA) Award in Musical Score/Composer category (Black Angels by Cynthia Wells). Other prizes and awards include the All-Polish Composers’ Competition in Lódz, Poland (1985, aennea for guitar solo); the All-Polish Composers’ Competition in Kraków, Poland (1988, Motet for six vocal soloists), and The Pierre Boulez Canadian Composers Competition in Halifax, Nova Scotia (1991, Horror vacui — triptych for strings named by Pierre Boulez in third place). Grella-Mozejko is also recipient of the Social Sciences and Humanities Research Council of Canada Doctoral Fellowship (2000-02) as well as the University of Alberta Beryl Barns Award, Walter H Johns Fellowship, Andrew Stewart Memorial Graduate Prize, Marie Louise Imrie Graduate Award and, in 2004, a professional development grant awarded by the Canada Council for the Arts.

Presented in twenty-two countries in centres such as Antwerp, Athens, Basel, Berlin, Bilbao, Dublin, Geneva, Kassel, Kaunas, Kraków, London, Los Angeles, Lausanne, Mexico City, Montréal, New York, Ottawa, Paris, Prague, Princeton, St Petersburg, Seoul, Toronto, Turin, Ulaanbaatar, Utrecht, Vancouver, Vienna, Warsaw and Zürich, in recent years, Grella-Mozejko’s music has been commissioned, played and recorded by symphony and chamber orchestras in Canada and abroad (including orchestras in Edmonton, Halifax, Kraków, Kyiv, Regina, Scarborough, Wroclaw and Polish Radio Orchestra, Warsaw) as well as by such outstanding performers as the Bozzini, Penderecki and Szymanowski String Quartets, ARA Ensemble, Duo Dilemme, Duo Levent, Duo Majoya, Edmonton Saxophone Quartet, Ensemble MW2, The Hammerhead Consort, Hermes Ensemble, Mexico City Woodwind Quintet, Motion Ensemble, St Crispin’s Chamber Ensemble; flautists Chenoa Anderson, Karin Aurell, Iwona Glinka, Isabelle Schnöller; clarinettists Jean-Guy Boisvert and Harry Sparnaay; saxophonists Laurent Estoppey, Charles Stolte, William H Street, Andreas van Zoelen; violinist Elena Denisova, organists Marnie Giesbrecht, Carson P Cooman, Stillman Matheson, Stanisław Moryto; pianists Barbara Pritchard, Sylvia Shadick-Taylor, Kathleen Supové, Roger Admiral, Alexei Kornienko, Joachim Segger, and Daan Vandewalle, to mention just a few.

His works have appeared in Canada and Europe on Acte Préalable, Arktos, ATMA Classique, Centrediscs, CLEF Records, CML, Eclectra, New Music North, Prairie Sounds and edition zeitklang labels; have been broadcast and published in Canada, Europe and USA; and performed at numerous festivals and concert series across North America, Europe and Asia. A voting member of the Canadian Music Centre, General Manager of the Edmonton Composers’ Concert Society, Grella-Mozejko is also producer of the New Music Alberta concert series, and current editor of The Alberta New Music & Arts Review (which he founded in 1997). As a CD producer, he has a dozen releases to his credit, featuring works by almost seventy Canadian and international composers.