Ian Cousins received his Bachelor of Economics degree at Monash University in 1969, and from 1972 to 1975 attended the National Theatre Opera School in Melbourne.  In 1975, he represented Australia in the Pan Pacific finals of the Metropolitan Opera Auditions and won the Victorian State Final of the ABC Instrumental and Vocal Competition.

Ian Cousins was a principal baritone with the Victoria State Opera from 1975 until that company recently merged with the Australian Opera to form Opera Australia.  As well as performing in almost all the main seasons, he also appeared in the VSO's contemporary music theatre seasons and many of the regional tours.  His many roles include both Don Alfonso and Guglielmo in Cosi fan tutte, Morales/Dancairo in Carmen, Valentin in Faust, Figaro and Doctor Bartolo in The Barber of Seville, Sharpless in Madama Butterfly, the Marquis and Germont in La Traviata, Talbot in Maria Stuarda, and Zurga in The Pearl Fishers.

He has also performed the roles of Count Almaviva in The Marriage of Figaro with the West Australian Opera, and various performances with the State Opera of South Australia. For Chamber made Opera he performed the role of Alfredo Menotti in their production of Lacuna, and sang Mahler's Songs of a Wayfarer for the Australian Ballet's seasons in both Sydney and Melbourne. He performed in A Morning at the Opera for the Queensland Symphony Orchestra, and for the 1989 Spoleto Festival, Faber in Tippett's The Knot Garden. For the Port Fairy Folk Festival, Ian Cousins performed the role of Smirnov in The Bear.

Ian Cousins has appeared regularly with prominent choirs and orchestras including the Royal Melbourne Philharmonic Choir, Melbourne Chorale, Geminiani Chamber Orchestra and the Australian Chamber Soloists, performing Dreyfus'  Galgenlieder and Ravel's  Chansons Madécasses as part of the ABC's Mahler in Vienna Festival. Other concert appearances have included performances for groups such as Rantos Collegium (Melbourne Chamber Orchestra), the Victoria Chorale and the Monash and Melbourne University Choral Societies, in many works including  Shostakovich's 14th Symphony, Brahms' Ein Deutsches Requiem, Adamis' In Bethlehem, Faure's Requiem, Durufle's Requiem, Beethoven's Symphony No. 9, Haydn's Nelson Mass, Scarlatti's St. Cecilia Mass, the title roles in concert performances of Berg's Wozzeck and Vaughan Williams' The Pilgrim's Progress.

Ian Cousins has performed Orff's Carmina Burana on many occasions, and his performances of this role have been widely acclaimed.  He also performed as a principal artist in the highly acclaimed Oz Opera production of The Barber of Seville, in a national tour which saw him perform in regional and capital cities throughout Australia.

Ian is well known as a recital and concert performer, singing teacher, adjudicator and examiner for various music organisations throughout Australia.