Middle Tennessee (2-3) never trailed in the Conference USA opener for both teams.
Each squad exchanged touchdowns in the first quarter, and each made subsequent field goals, and the score was tied at 10. But O'Hara's 4-yard TD run capped a 6-play, 53-yard drive that put the Blue Raiders ahead for good with 3:42 left before halftime.
O'Hara capped the scoring with a 36-yard touchdown pass to Zack Dobson with 12:43 to play.
Moffatt picked off Isaiah Green on Marshall's (2-3) first play of its second drive. He picked off Green again on the Thundering Herd's second-to-last drive of the contest.
Green threw for 365 yards and a touchdown but had three interceptions.
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