AMES, Iowa -Todd Blythe caught two touchdown passes from Bret Meyer to key a 31-point second half and Iowa State held on during a wild final sequence to beat Colorado 31-28 on Saturday.

Iowa State (3-8, 2-5 Big 12) rallied from a 21-0 halftime deficit to win for the second straight week - the Cyclones' first two-game winning streak in league play since they won four in a row in 2005.

But the Cyclones weren't sure of the victory until time ran out just before Colorado's Kevin Eberhart made a 55-yard field goal that would have tied it.

Colorado (5-6, 3-4) had no timeouts and rushed its field goal unit onto the field with the clock running down. Eberhart made a 50-yarder, but the Buffaloes were penalized 5 yards for delay of game for snapping the ball before it was blown into play.

The officials marked off the penalty and Colorado lined up again. Eberhart made the longer kick, but the officials ruled the final second had ticked off before the ball was snapped.

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 the game-clinching score with 4:07 left.

Colorado appeared to have recovered from its 55-10 loss to 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.

They still managed to get within three on Cody Hawkins' 9-yard touchdown pass to Scott McKnight with 2:40 to play. The Colorado defense then forced a punt and Hawkins completed two passes to set up the final flurry of activity.

Hawkins finished 23 of 40 for 262 yards and two TDs and had three passes dropped. He also scored a touchdown.

Meyer and Blythe 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.

Two penalties then 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 Hakwins' late TD pass.

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. Jesse 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.