Gardner made her stage debut Off-Broadway in Jerry Herman's musical review Nightcap (1958)[2][3] before her breakout turn as Luisa in the original cast of The Fantasticks in 1960.

[4][5][6] Other off-Broadway credits include The Cradle Will Rock (1964), To Be Young, Gifted, and Black (1969), Jacques Brel is Alive and Well and Living in Paris (1972), Steel Magnolias (1987), Wings (1993), and The Foreigner (2004).

[7][8] Gardner made her Broadway debut in the short-lived musical (65 performances) A Family Affair in 1962 as Sally Nathan.

[9][10] She was featured in a brief 1963 revival of Pal Joey as Linda English[11] and replaced Susan Watson soon after the opening of Ben Franklin in Paris in 1964.

In 2002, she appeared in her one-woman revue Try to Remember: A Look Back at Off-Broadway at the Sullivan Street Playhouse in New York City on Saturday evenings.