Sam Houston (3-3, 2-0 Southland Conference) jumped out to an early 14-0 lead and held on to knock off the Cowboys (3-2, 1-1) who were ranked No. 4 in the FCS national polls. SHSU was unranked.
Johnson, who rushed for 190 yards on 11 carries and threw for 192 yards, accounted for all but 104 of SHSU's 486 total yards.
The Bearkats led 21-7 at the half following Johnson's 73-yard scoring sprint with 2:14 remaining in the second quarter. Johnson passed to Yedidiah Louis for a 22-yard score to start the third and ran 67 yards for another score and a commanding 35-7 lead.
Daniel Sams rushed for 130 yards and one touchdown on 20 carries for the Cowboys.