Penske Racing announced Saturday it plans to put Allmendinger in Nationwide Series road course events at Road America and Mid-Ohio Sports Car Course.
"With his stock car experience and his road course experience, we think this is the perfect opportunity for him and for the team," team owner Roger Penske said.
This weekend, Allmendinger is driving in the Detroit Grand Prix races and insists he doesn't have a preference between IndyCar and NASCAR racing.
"I'm just happy to have the opportunity to drive something," he said.
Allmendinger has been out of NASCAR since being suspended for testing positive for Adderall last year.
Penske fired him, but gave him another chance with a part-time schedule in the IndyCar series.
"There's nothing I could do to come even close to repaying him," Allmendinger said. "So I just try to give everything I've got and hopefully it's enough."
Allmendinger finished seventh in the Indianapolis 500 on Sunday, missing a shot at a better outcome because his seat belt became undone.
"It's kind of tough when you're leading the race and your belt just falls off," he said. "I tried to fix it down the back straightaway into the corner, and it wasn't going to be fixed by me. At that point, all you can do is pit and try to make up for it."
That put Allmendinger off the pit cycle, and forced him to stop for gas twice far in advance of the rest of the field.
Allmendinger is scheduled to drive the June 22 Road America race in Elkhart Lake, Wis., and the Aug. 17 road course race in Lexington, Ohio.
"It's actually easier going back to stock cars right now," he said.