A 6-foot-5, 290-pound player, Megginson is a four-star in the 2015 class.
The Cyclones had been in touch via graduate assistant Derek Day, who put head coach Paul Rhoads on the phone for the scholarship offer.
ISU has invited Megginson to a Junior Day but he's not sure he'll get to Ames for it.
"Hopefully for a visit at some point," he said.
In the past week, Ohio State, Penn State and Michigan State have offered.