Oklahoma State coach Mike Gundy wasn't sure his team had enough gas left in the tank as Saturday's game stretched over four hours long.

But that old football adage of just making one play saved his Cowboys.

Iowa State reached the 4-yard line and was threatening to force overtime but Oklahoma State sophomore cornerback A.J. Green outwrestled Cyclones senior Marchie Murdock to intercept the ball in the end zone with 32 seconds left. The big defensive play gave the No. 15 Cowboys a 49-42 victory over No. 21 Iowa State in Big 12 play at Ames, Iowa.

"The guys were very resilient," Gundy said.

"We knew this was going to be a difficult game. I had concerns during the week, not about our preparation mentally, but being a little bit fatigued after last week's game (against Oklahoma) because of the total number of plays."

Senior quarterback Mason Rudolph passed for 376 yards and three touchdowns and sophomore running back Justice Hill rushed for 134 yards and three scores for the Cowboys (8-2, 5-2 Big 12), who scored 15 consecutive fourth-quarter points to overcome an eight-point deficit.

Redshirt freshman receiver Dillon Stoner caught the go-ahead touchdown, senior wideout Marcell Ateman had two scoring receptions and junior receiver Jalen McCleskey had five receptions for 109 yards.

Green's interception allowed Oklahoma State to win for the fifth time in six games. The Cowboys finished the road part of their schedule with a 6-0 mark and have won 16 of their past 18 true road contests.

Sophomore running back David Montgomery rushed for 105 yards and three touchdowns for the Cyclones (6-4, 4-3), who have lost back-to-back games. Senior receiver Allen Lazard had nine receptions for 126 yards and two touchdowns, but Iowa State fell for the sixth straight time against the Cowboys.

"It's a gut-wrenching loss. It's not easy, but college football isn't easy," Iowa State coach Matt Campbell said.

"It's a game of inches and our job is to win every inch, and we came up a little bit short today. I give credit to Oklahoma State, they're obviously a really good football program, and they made more plays than we were able to make by the end of the day."

The Cyclones played the second half without senior quarterback Kyle Kempt, who suffered an undisclosed injury and watched from the sidelines in street clothes. Kempt completed 12 of 18 passes for 101 yards and one touchdown before departing.

The injury left Iowa State's quarterbacking to redshirt freshman Zeb Noland (263 yards and the late interception) and senior middle linebacker Joel Lanning, the team's former starting signal caller. Lanning displayed that the right arm still works well when he threw a 22-yard touchdown pass to Lazard, who made an acrobatic grab to give the Cyclones a 35-31 advantage with 14:13 remaining in the game.

"I knew if that moment came where he threw me the pass, then I had to make sure I caught it," Lazard said of a catch in which he tipped the ball with his left hand while being defended tightly and corralled it with his right just before falling out of bounds.

Sophomore Matt Ammendola kicked a 41-yard field goal with 9:43 to play to bring Oklahoma State within one point. But Montgomery found the end zone on a 4-yard run just 65 seconds later to give Iowa State a 42-34 edge.

The eight-point lead evaporated when the Cowboys converted a third-and-22 with Ateman jumping high above Cyclones junior cornerback D'Andre Payne to make a 30-yard touchdown catch with 5:55 remaining. Hill took a direct snap and ran in the two-point conversion to tie it at 42, and Oklahoma State went ahead to stay when Rudolph connected with Stoner on a 19-yard touchdown pass with 3:47 remaining.

"They're an interesting team," Gundy said.

"They've been that way the last couple years, and especially this year. There's just not enough flash when you watch them to make people think anything other than, 'How are they as successful as they've been?' Then you play them and they're just good at what they do. They don't make a lot of mistakes."

Iowa State started the game strong by scoring two touchdowns in the first 10-plus minutes to take a 14-0 lead. The Cyclones drove 73 yards on 11 plays to open the game with Kempt tossing a 14-yard scoring pass to Lazard, and Montgomery tacked on a 22-yard scoring run with 4:52 left in the quarter.

Rudolph threw a 21-yard touchdown pass to Ateman to get the Cowboys on the board with 1:31 left in the stanza. Hill scored on a 9-yard run to tie the score with 12:38 left in the first half and added a 2-yard touchdown run four-plus minutes later to give Oklahoma State a 21-14 lead.

Iowa State knotted the score at 21 on Lanning's keeper with 22 seconds remaining.

Oklahoma State took a 24-21 lead on Ammendola's 35-yard field goal with 10:17 left in the third quarter. The Cyclones responded by taking a 28-24 lead on Montgomery's 3-yard run with 6:57 remaining before the Cowboys regained the lead at 31-28 on Hill's 1-yard run with 1:27 to play, which came after Rudolph's 81-yard pass play to McCleskey.

NOTES: Cyclones senior WR Allen Lazard became the second player in school history to top 3,000 receiving yards. Lazard has 3,071 and is closing in on first-place Todd Blythe (3,096 from 2004-07). ... Cowboys senior FS Tre Flowers was ejected for targeting for a hit on Iowa State senior WR Trever Ryen with 8:53 remaining and will miss next Saturday's first half against Kansas State. ... Lazard is the active FBS leader with a catch in 45 consecutive games, while Oklahoma State senior WR James Washington is second (42) in that category despite being held to one catch. ... Cowboys sophomore RB Justice Hill has topped 100 yards rushing in six of the past seven games. ... Iowa State senior MLB/QB Joel Lanning had five tackles to reach 99 for the season, while also throwing his 20th career touchdown pass. ... Oklahoma State senior QB Mason Rudolph has eight 300-yard passing games this season and 20 in his career.