His television writing and producing credits include The Naked Truth, Party of Five, Sex and the City, Gilmore Girls, The O.C., Grey's Anatomy, Looking, and Scandal .

As part of this series, he co-created the Marvel characters Kate Bishop, Hulkling, Iron Lad, Patriot (Eli Bradley), Speed, and Wiccan.

For DC Comics, Heinberg co-wrote JLA: Crisis of Conscience with Geoff Johns (art by Chris Batista), and re-launched Wonder Woman with artists Terry and Rachel Dodson.

Heinberg acted in the Broadway cast of Laughter on the 23rd Floor and appeared off-Broadway in Hello Muddah, Hello Fadduh and the Vineyard Theatre's production of Bob Merrill's Hannah...1939 starring Julie Wilson.

After co-writing a 5-issue arc of DC Comics's JLA with Geoff Johns, Heinberg and artist Terry Dodson relaunched Wonder Woman following the Infinite Crisis limited series.