Tennant trained at the NATIONAL BALLET SCHOOL and upon graduation was hired into the company at the principal dancer level, making her debut as Juliet in John Cranko's version of the full-length Prokofiev ballet Romeo and Juliet, later produced for CBC-TV by Norman CAMPBELL. In rapid succession during her second season, Tennant added many other leading roles to her repertoire - Swan Lake, Giselle, The Nutcracker - and with the retirement of Lois SMITH was quickly adopted by critics and her adoring public as the company's de facto prima ballerina. Tennant danced the title role in Campbell's Emmy Award-winning 1968 CBC-TV production of Cinderella and continued to excel in the great 19th-century classics, gaining even wider renown when she became the National Ballet's first Princess Aurora in its 1972 staging by Rudolf Nureyev of The Sleeping Beauty, another Emmy-winning program in Campbell's production for CBC-TV. Tennant's repertoire also expanded to embrace an enormous variety of roles, including many works created for her superb talent as a dance-actress. Although in mid-career Tennant suffered a potentially ruinous knee injury, she took the opportunity of almost a year away from the stage to write a children's book and have a daughter before making a triumphant return. Two of her most celebrated later roles were as Titania in Frederick Ashton's The Dream and as Tatiana in Cranko's Onegin.

During her long dancing career, Tennant was partnered by many of the greatest male dancers of the day, among them Rudolf Nureyev, Mikhail Baryshnikov, Anthony Dowell, Fernando Bujones, Richard Cragun and Peter Schaufuss. In what many considered a premature retirement in 1989, Tennant bowed out by giving several dazzling farewell performances of Juliet, the role that had established her reputation 24 years earlier, followed by a special tribute gala with visiting guest artists.

Since retiring from the National Ballet Tennant has remained very active in the dance world and performing arts in general, choreographing, hosting, narrating, writing, teaching and directing. She expanded into the theatre as associate director and choreographer at Toronto's CANADIAN STAGE COMPANY and TARRAGON THEATRE and was an actor and dancer at the SHAW FESTIVAL in the 1992 season. In 1994 she choreographed Cyrano at the STRATFORD FESTIVAL. Tennant also devised and performed a dramatic dance piece, Maud, drawn from the journals of Lucy Maud MONTGOMERY, and co-wrote and performed Choice and Chance Encounters with clarinetist James Campbell and jazz pianist Gene DiNovi at the Festival of the Sound and the Muskoka Festival in Ontario. In 1995 she shared the title role with Nicholas Pennell in the Rhombus Media film Satie and Suzanne.

Increasingly, the focus of her work has been with CBC-TV. Tennant was host, creative consultant and writer of a show called Sunday Arts Entertainment for three seasons. Her first venture as a television producer was a 1995 CBC/SRC co-venture, Salute to Dancers for Life/Danser Pour La Vie, followed by a 1996 special about modern dancer Margie GILLIS and another featuring Karen KAIN in 1999, which went on to win an International Emmy Award. More recently she has moved from producing into directing dance films and videos.

Tennant is the author of two children's books, On Stage, Please and The Nutcracker. She was appointed an Officer of the Order of Canada (1975), was promoted to Companion of the Order of Canada (2004), and is the recipient of many awards and honorary degrees, including the Walter Carsen Prize for Excellence in the Performing Arts (2004) and the Governor General's Performing Arts Award (2004).