Montgomery is noted for her storyboard work on animated television series and direct-to-DVD films. She directed Green Lantern: First Flight, Superman/Batman: Apocalypse, Justice League: Doom, and the animated film Wonder Woman. Montgomery also co-directed Justice League: Crisis on Two Earths and Batman:Year One with Sam Liu and worked on the American television series Young Justice.
In 2012, Montgomery returned to Nickelodeon and the Avatar franchise as a supervising producer and storyboard artist for The Legend of Korra. She currently works as an executive producer and co-showrunner on the animated series Voltron: Legendary Defender alongside Joaquim Dos Santos.