The actor, who is best known for his starring role as telepathic police officer Matt Parkman on Heroes, will appear in David Shore's legal drama Doubt.
Grunberg will play Mark, the older brother of protagonist Vince. His character has a development disability as a result of a childhood accident and is described as "high-functioning" by production insiders.
Mark works as a receptionist at police officer-turned-lawyer Vince's office, and has every faith that his sibling can save the world.
Grunberg's other recent TV credits include The Client List, Psych and Hawaii Five-0.
He joins Sons of Anarchy's Rockmond Dunbar, who will play Vince's former partner from his days in the police force.
Doubt's pilot episode will be directed by Thomas Schlamme (Pan Am, The West Wing).
House creator Shore is writing the script, and will be executive producer as part of his deal with Sony Pictures Television.
US TV pilots for the 2013-14 season - photo gallery:
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