It was the 22-year-old right-hander's second dominant start in a week after he tossed five hitless innings against Beloit on July 17.
Tepera (9-4) did not allow a hit in this one until Leonardo Gil hit a roller up the third-base line with one out in the fifth. He retired the next two batters to lower his ERA to 3.14.
The Jays' 19th-round pick in last year's Draft walked two, struck out two and turned a three-run lead over to Scott Gracey, who retired all six batters he faced.
Matt Wright was the second reliever out of the Lugnuts' bullpen and, after issuing a leadoff walk, struck out the next three batters to retire the side in the eighth. Nestor tossed a 1-2-3 ninth for his fourth save.
In taking three in a row from the Cougars, Lansing allowed only 14 hits to a team that had won nine of its previous 10 games.
The Lugnuts totaled only four hits, but Kevin Ahrens and Sean Ochinko hit solo homers that proved more than enough run support for Tepera and the bullpen.