McBain was born in Riverside, California. She was educated at San Bernardino Valley College in California and studied at California State University. She was always passionate about art and history, so her father both encouraged her, and helped her to write her first historical romance.
Her first book, Devil's Desire, was published in 1975 by Avon, joining her to a new generation of romantic writers, such as Kathleen E. Woodiwiss. Together they changed the style of the historical romance. Devil's Desire and her second novel Moonstruck Madness, each sold over a million copies.