Keys scored 43 unanswered points and stunned Hugo, 50-26, Friday in Hugo to win its first playoff game since 2012.
The Cougars, who improve to 4-7 overall under first-year head coach Adam Hass, trailed 26-7 in the first half and 26-14 at halftime.
"Our MO all year has been don't give up," Hass said. "We didn't give up. We came out slow in the first half, and in the second half we were all on board."
Keys advances to next week's second round where it will face Cascia Hall on Nov. 20 in Tulsa. The Cougars suffered a 34-21 loss to Cascia Hall to close out the regular season.
The Cougars had four touchdowns on the ground and three through the air.
"We were more physical in the second half," Hass said. "We just ran the ball, played hard and came alive in the second half."
"This is big for the program to get a playoff win," Hass added. "We've been talking about it all year about how we're going to be a playoff team. Things didn't go our way a lot this season and we had a lot of hurdles and things like that, but we earned it."
Cascia Hall, ranked fourth, has won its last seven games and is 8-1 on the season. The lone loss came to Holland Hall in week two.