AMES, Iowa (AP) -- Iowa State coach Gene Chizik wasn't sure what happened at the end. Neither was Colorado coach Dan Hawkins.
They weren't alone.
Everyone in the stadium watched in confusion as Colorado's Kevin Eberhart first made a 50-yard field goal that was negated, then made a 55-yarder that was called off because time had run out, allowing Iowa State to escape with a 31-28 victory on Saturday.
"I've been in a lot bizarre games," Hawkins said. "This might be close to the top."
The wild sequence came after Iowa State (3-8, 2-5 Big 12) matched its biggest comeback since a 1989 win over Missouri by scoring 31-second half points to erase Colorado's 21-0 halftime lead.
Colorado (5-6, 3-4) cut the lead to three on Cody Hawkins' 9-yard touchdown pass to Scott McKnight with 2:40 left. The Buffaloes' defense held and Colorado got the ball at its own 28 with 46 seconds left and no timeouts.
Hawkins drove them to the Iowa State 33, but Tyson DeVree couldn't get out of bounds on a third-down reception, so the field goal unit had to rush onto the field. Eberhart's kick fluttered through the uprights, but Colorado was called for delay of game for snapping the ball before it was blown into play.
The officials marched off 5 yards, put a second on the clock and Colorado lined up again. Eberhart made the longer kick, but the officials ruled time had expired before the ball was snapped and the Buffaloes stomped off the field as Iowa State fans swarmed out of the stands.
"I'm not sure what happened, but we won," ISU linebacker Jesse Smith said. "That's all that matters."
Chizik said he never got an explanation from the officials, but didn't seem to mind.
"Time expired," he said. "That was the bottom line."
Hawkins said he'll seek an interpretation from the Big 12 office and insisted, "We snapped it before it went to zero."
Todd Blythe caught two touchdown passes from Bret Meyer to key Iowa State's rally, which gave the Cyclones their first two-game winning streak in conference play since they won four in a row in 2005.
Alexander Robinson carried 29 times for 127 yards and two touchdowns for Iowa State, including a 9-yard scamper on an option pitch from Meyer for what turned out to be the decisive score with 4:07 left.
Colorado appeared to have recovered from its 55-10 shellacking by Missouri a week ago by dominating the first half. But the Buffaloes self-destructed with major penalties and a critical fourth-quarter fumble, and Eberhart missed a 43-yard field goal that would have tied it at 24 with 8:39 remaining.
"You really can't talk about what happened on that last play or last series because we had plenty of opportunities to win this football game," Colorado defensive tackle George Hypolite said.
"We dropped some balls, missed some tackles and let them make some big plays. The game shouldn't have come down to a last-second field goal."
Meyer and Blythe, who came to Iowa State together in 2003, hooked up four times for 124 yards in their final home game.
Blythe's 12-yard touchdown grab, when the 6-foot-5 receiver bent over like an infielder going for a grounder to catch the ball, drew Iowa State to 21-14. The Cyclones tied it when Blythe beat two defenders on a 55-yard play to tie it.
"I can't think of a script any better the way we came back," Blythe said.
Two penalties helped set the Cyclones up for Bret Culbertson's tie-breaking 24-yard field goal with 12:21 left.
Iowa State started at the Colorado 45 after the Buffs were penalized 15 yards for interfering with Blythe on a punt catch. A pass interference penalty on fourth down kept the drive alive and the Cyclones got close enough for Culbertson to make his kick into the wind.
Alvin Bowen's recovery of Hugh Charles' fumble at the Colorado 43 set up Robinson's final touchdown, which enabled the Cyclones to withstand Cody Hakwins' late TD pass.
Hawkins finished 23 of 40 for 262 yards and two touchdowns and had three passes dropped. He also scored a touchdown.
Colorado scored twice in the final 2:49 of the second quarter to open a 21-0 halftime lead, then stalled going against the wind in the third quarter. The Buffaloes managed only 28 yards in 13 third-quarter plays and ended up giving Iowa State a spark when a fourth-down gamble failed.
Iowa State declined a holding penalty to leave Colorado with a fourth-and-1 at its own 43 on the first series of the quarter. Smith stopped Demetrius Sumler for no gain and three plays later, Robinson ran 13 yards for a touchdown, breaking two tackles and carrying cornerback Benjamin Burney the final 3 yards.
"As soon as something good happened, it was downhill from there," Meyer said. "Obviously you don't want to get down like that. But it's great to go out like we did."