A 6-yard touchdown run by Gray followed up with a 41-yard field goal by David Arauz gave Hoover (1-0) a 10-0 lead with 4:22 left in the first quarter.
Monte Vista struck back on the following possession with a 32-yard pass from Tre Owens to Jalonte Jones that set up Jaccob Jardim's 18-yard touchdown run.
Following a Cardinals punt, the Monarchs capped a 98-yard drive with a 2-yard quarterback keeper by Owens, giving Monte Vista a 13-10 lead at halftime.
The second half was all Hoover as Gray added four more touchdowns during a 27-13 scoring run that sealed the victory.
Next week the Cardinals host Francis Parker while the Monarchs visit inner-city foe Steele Canyon.