The Bobcats (2-0), who opened with a win over Penn State, have won eight of nine dating back to last season.
Tettleton passed for 257 yards and also ran for 18 yards and a score, and Blankenship had 168 rushing yards on 27 carries.
The Aggies (1-1) trailed just 21-17 as late as the third quarter when Ohio's Matt Weller hit a 37-yard field goal that sparked 24 unanswered points for the Bobcats to put the game out of reach. Weller made 3 of 4 field goals to become the school's all-time leading scorer.
Nate Carpenter scored on a 22-yard interception return during that span.
Andrew Manley threw for 132 yards with a touchdown and an interception for the Aggies.