Örjan Ramberg started his acting career in musicals with leading parts in the original Swedish stagings of Hair (1971) and Jesus Christ Superstar (1972; opposite, among others, Agnetha Fältskog (later of ABBA) as Mary Magdalene).

On stage, Örjan Ramberg has had both leading and supporting parts: in Nathanael West's En kall miljon (A Cool Million), Ben Jonson's Alkemisten, Marivaux's Paradisbarn, Bulgakov's Mästaren och Margarita, Lars Norén's Natten är dagens mor, Margaretha Garpe's Till Julia, Lessing's Emilio Gallotti, in the stage adaptation of Astrid Lindgren's Emil i Lönneberga (children's theatre production), Shepard's En riktig västern, Shakespeare's Romeo and Juliet, Sommar (Summer) written and directed by Lars Norén, Beaumarchais' Figaros Bröllop (The Marriage of Figaro), Federico García Lorca's Blodsbröllop (Blood Wedding), Shakespeare's Lika för lika (Measure for Measure), Euripides' Medea (directed by Lennart Hjulström), Shakespeare's Så tuktas en argbigga (The Taming of the Shrew) children's play Mio, min Mio (based on the novel by Astrid Lindgren) and in Alfred de Musset's Lek ej med kärleken (On ne badine pas avec l'amour ), among others.

He appeared as Charles Condomine in Noël Coward's Min fru går igen (Blithe Spirit) (2005), in the co-Nordic production of the Sami staging of Ibsen's Kungsämnena (The Pretenders) and in Shakespeare's Macbeth (directed by Staffan Valdemar Holm) spring/autumn 2006.

On film and TV, he has appeared sporadically for example as the investigating photographer Harry Friberg in the Stieg Trenter-crime films for television (Lysande landning, Idag röd, Träff i helfigur) in 1987, as Chief Editor Schyman in Colin Nutley's thriller Sprängaren (aka Deadline/The Bomber), based on the book by Liza Marklund, and his recent supporting part as the bar pianist in TV-series Möbelhandlarens dotter (The Furniture Salesman's Daughter) (2006).

On 3 February 2007, John Caird's production of Strindberg's The Dance of Death premiered at the Royal Dramatic Theatre with Ramberg in the lead as The Captain (with both original parts of the play performed together; Dödsdansen I-II).