[3] From 2002 to 2012 and 2014 on, Grosz has starred as one half of the "Two Guys" for the Sonic Drive-In commercials alongside fellow improviser T. J.
[4][5] In 2020, it was reported that Sonic's commercials would be going in a different direction, but that the "Two Guys" series would continue to be part of the chain's advertising in some way.
Grosz worked as a writer for The Colbert Report from 2007 to 2010,[7] where he has appeared on screen at least four times: once as the Time-Travelling Brandy Thief, once as a version of himself on September 23, 2008,[8] once on May 13, 2010, to interrupt Stephen Colbert's attempt to introduce guest band The Hold Steady, only to perform the introduction himself, and on January 9, 2013, as McGnaw the Gluten-Free Beaver.
Grosz recurred on the HBO comedy series Veep, playing callous oil lobbyist Sidney Purcell over four of the first five seasons.
[12] On December 18, 2018, Grosz appeared on The Late Show with Stephen Colbert as Stephen Miller, Senior Advisor for policy to US President Donald Trump, in a sketch with Colbert about Miller's appearance on Face the Nation the previous Sunday.