Gloria Coates was born in Wausau, Wisconsin, and began composing and experimenting with overtones and clusters from an early age. Her studies took her from Chicago, Cooper Union Art School, NYC, and Louisiana (with a Master’s in Composition), to post graduate studies in composition at Columbia University, with both Alexander Tcherepnin (1899-1977) and Otto Luening (1900-1996) being important mentors.

Since 1969, Coates has lived primarily in Europe. The Polish Chamber Orchestra premiered her Music on Open Strings (Symphony No.1) under Jerzy Maksymiuk at Warsaw Autumn Festival in 1978, and in 1986 it was a finalist for the Koussevitzky International Award (KIRA). The piece achieved a "breakthrough" at Munich’s musica viva in 1980 as the first orchestral composition by a woman composer in the 34 year history of the festival.

Described by Mark Swed of the LA Times as possibly “the most obscure great composer of our time”, Coates has written numerous works including 17 symphonies, 10 string quartets, chamber music, solo and vocal music, musique concrète, and the chamber opera Stolen Identity. Her music has been performed at many festivals including MaerzMusik (Berlin), New Music America (New York), Other Minds (San Francisco), Dresden Music Festival, Warsaw Autumn, Avanti (Finland), the Hans Werner Henze Festival in Montepulciano, and Aspekte Salzburg.

Among the artists who have performed her work include the Kronos, Kreutzer, Spektral, and Jack String Quartets, the Bavarian Radio Symphony Orchestra, the Brooklyn Philharmonic, the Stuttgart Philharmonic Orchestra, the Milwaukee Symphony, the Vienna Radio Symphony Orchestra, and the St Paul Chamber Orchestra. In November 2018, she was invited by the BBC Scottish Symphony Orchestra for a concert of her Symphony Nos. 1, 7 and 11, conducted by Ilan Volkov.

Gloria is also a poet and painter, with many of her paintings used as the artwork for her recordings.