In 1964, Dr. Moguš was appointed assistant professor; in 1969, he was promoted to the position of associate professor; and in 1975, he became full professor. 1965-1992 (until his retirement), he held the post of Chairman of the Croatian Language Dialectology and History Department. In the 1970/71 and 1971/72 academic years, he was associate dean of the Faculty of Arts, Zagreb University. Starting from 1976, Dr. Moguš taught in the Graduate Linguistics Programme; and 1979-1985, he held the post of Director of the Graduate Linguistics Programme. 1983-1992, he chaired the Linguistics Institute of the Faculty of Arts.
Dr. Moguš lectured as visiting professor at the Cologne University in the 1969/70 and 1973/74 academic years, and at the Mannheim University in 1987/88. As professor of the Croatian Language Dialectology and History, he taught for many years at the Teachers College in Osijek and the Faculty of Arts in Rijeka.
Dr. Moguš participated in numerous national and international Slavic and onomastic conferences and congresses (Prague, Sofia, Warsaw, Bern, Zagreb, Krakow, Skopje, Ljubljana, Bratislava, Berlin, Leipzig, Belgrade, Helsinki, Santiago de Compostela, Washington). Moreover, he was a long-time member of the International Committee on Onomastic Sciences in Leuven, member of the International Committee for the Phonology and Phonetics of the Slavic Languages in Moscow, and President of the Inter-academy Committee on Onomastics in Zagreb. In 1997, he joined the membership of the Central European Academy of Science and Art.
In 1977, Dr. Moguš became associate member of the Croatian Academy of Sciences and Arts; and in 1986, its full member. 1985-1991, he carried out the duties of the Secretary of the Academy’s Department of Philological Sciences; 1991-1997, he held the post of Secretary-General; and 1998-2004, he was Vice-President of the Croatian Academy of Sciences and Arts. As from 1st January 2004, Prof. Dr. Moguš is the President of the Croatian Academy of Sciences and Arts.
In 1995, Dr. Moguš received honorary doctorate at the University of Rijeka; and in 1997, he furthermore received honorary doctorate at the Josip Juraj Strossmayer University of Osijek.
In 1990, Prof. Moguš was awarded the Božidar Adžija Prize for his scientific activity of great significance; while in 1994, he received the City of Senj Award. In 1996, he was decorated with the Order of the Croatian Star with the Effigy of Rudjer Bošković for scientific work. In 1998, Prof. Moguš was honoured with the Croatian State Award for Life Achievement. In 1998, the Republic of Poland decorated him with the Officers' Cross for Merits, and the Republic of Slovakia with the Ljudevit Štur Golden Medal. In 2001, Prof. Moguš was awarded the Golden City Arms of Split; whilst in 2004, he became honorary citizen of the City of Senj. In 2005, he was awarded the Golden Coin of the Vukovar-Srijem County, and in the same year, he received the Chakavian Assembly’s Award for Life Achievement in Pula. In 2007, Prof. Moguš was decorated with the Order of Duke Branimir with Ribbon, and in 2009, with the Order of Ante Starčević for his contribution to the continuation and development of the Croatian nation-building policy by the means of establishing and building of the Croatian independent state. In 2010, Prof. Dr. Moguš was elected honorary fellow of the Catholic Faculty of Theology in Đakovo.
From 1998 up to the present, he has been performing the duty of the President of the Croatian UNESCO Commission.
Dr. Moguš published, alone or in co-editorship (abbr. c-e.): a) scientific monographs: Današnji senjski govor, Fonološki razvoj hrvatskoga jezika, Čakavsko narječje, Antun Mažuranić, Azbukoprotres Save Mrkalja (c-e.), Križanićeva hrvatska gramatika, Zakon trsatski (c-e.), Povijest hrvatskoga književnoga jezika (Croatian, English and German edition), Hrvatski jezik u Hrvatskom saboru (c-e.) (Croatian and English edition), Ivan Mažuranić: Smrt Smail-age Čengića (c-e.); b) four computer concordances of the works of Croatian writers (c-e.); c) six dictionaries: Croatian-English (c-e.), Croatian-French (c-e.), Hrvatski čestotni rječnik (c-e.), Rječnik Marulićeve Judite (c-e.), Slownik polsko-chorwacki (c-e.), Senjski rječnik; d) critical editions of two works by Marko Marulić (Judita and Naslidovanje); e) the manual Hrvatski pravopis (c-e.) (eight editions so far); f) approximately 270 scientific and expert discussions and articles on the Croatian and Slavic Philology and Linguistics in over 60 domestic and foreign journals.
Dr. Moguš acted either as editor-in-chief or as co-editor in publishing several journals and editions, such as: Bulletin of the Institute for Linguistics of the Faculty of Arts (Bilten Zavoda za lingvistiku Filozofskog fakulteta), Bulletin scientifique, Monographs of the Institute for Slavic Philology (Radovi Zavoda za slavensku filologiju), Croatian Dialectologists’ Collection (Hrvatski dijalektološki zbornik), Language (Jezik), Early Croatian Writers (Stari pisci hrvatski), Works of the Croatian Academy of Sciences and Arts (Djela Hrvatske akademije znanosti i umjetnosti), The Paulists’ Collection (Pavlinski zbornik), The Senj Glagolitic Circle 1248-1508 (Senjski glagoljaški krug 1248-1508), and Cithara octochorda. As Secretary-General of the Croatian Academy (1992-1998), he furthermore edited the Chronicle of the Croatian Academy of Sciences and Arts (Ljetopis Hrvatske akademije znanosti i umjetnosti); and as Vice-President, The Memorials: 140 years of the Croatian Academy of Sciences and Arts (Spomenice: 140 godina Hrvatske akademije znanosti i umjetnosti). He is the linguistic editor of the Croatian Biographic Lexicon (Hrvatski biografski leksikon), and a co-editor of the Dictionary of the Croatian Standard Language from the Croatian National Revival to I. G. Kovačić (Rječnik hrvatskoga književnoga jezika od preporoda do I. G. Kovačića) as well as of the Complete Works of Marko Marulić (Sabrana djela Marka Marulića).
Until his retirement in 1992, as the chief researcher at the Institute for Linguistics of the Faculty of Arts, Prof. Moguš was the project manager of the scientific project entitled The Study of the Croatian Standard Language (Proučavanje hrvatskoga književnoga jezika). At present, he is conducting the scientific project The Study of the Croatian Dialects (Proučavanje hrvatskih dijalekata) as the chief researcher at the Linguistic Research Institute of the Croatian Academy of Sciences and Arts.