Oklahoma State opened Big 12 Conference play by splitting a doubleheader against Missouri Saturday at Taylor Stadium, earning a 3-2 win in the first game before dropping a 4-1 decision in the nightcap.The Cowboys (13-9) rode the left arm of Andrew Heaney and the ninth inning heroics of Mark Ginther for a dramatic victory in the opener.With OSU trailing 2-1 and down to their final out in the ninth, Ginther delivered a two-run home run off Mizzou closer Jake Walsh to put the Cowboys on top.The Tigers (12-8) threatened in the bottom of the ninth, but Heaney kept them off the scoreboard and picked up his third-straight complete game win to improve to 5-1 on the season.In what would prove to be a pitchers' duel throughout, OSU took an early lead in game one. After a two-out double by Robbie Rea and a single by Ginther, Trey Whaley stepped to the plate and delivered a single to give the Cowboys a 1-0 advantage in the top of the first.That lead held until the fifth when Heaney had a streak of 24.1 scoreless innings snapped by a two-out RBI single by Dillon Everett that tied the score at 1-1.Mizzou plated the go-ahead run in the next inning when Conner Mach singled, stole second and then scored on a single by Blake Brown.That lead looked like it would hold up as Missouri starter Rob Zastryzny had a career day with 12 strikeouts.However, Heaney matched the Tigers' starter to keep OSU in the game. The Cowboys' junior southpaw, who leads the NCAA in strikeouts this season, tied a career high with 13 strikeouts and did not issue a walk.In the decisive ninth, Jared Womack singled with one out, but Rea flied out for the second out of the inning. That brought up Ginther, who deposited a 1-1 pitch from Walsh over the wall in left-center field. The round tripper was Ginther's fourth of the season, tying him for the team lead.In the bottom of the inning, Heaney retired the first two Tiger hitters. Up next, Ben Turner singled and was followed by Eric Garcia, who also singled. But pinch runner Jake Ivory got caught in a rundown between second and third base and was tagged out to end the game.The second game saw the Cowboys manage just one unearned run against MU starter Blake Holovach, who improved to 4-0 on the year by allowing just five hits in 8.2 innings. Walsh again came out of the bullpen in the ninth, and this time he earned the save, his seventh of the season.OSU starter Chase Stevens would not make it out of the first inning in the nightcap. The right-hander walked the first two Tiger hitters and gave up a one-out single to load the bases. He then struck out Turner, but his third walk, this one to Eric Garcia, brought home Mizzou's first run.After falling behind to the next batter 2-0, Stevens' day was done. Blake Barnes came on and promptly surrendered a two-RBI single to Scott Sommerfeld to give the Tigers a 3-0 advantage.Mizzou's final run came in the fourth as Barnes limited any real further damage, working six innings and allowing only one run on seven hits.However, the Cowboys' offense could not get going against Holovach. Their only run came in the seventh when Gabe Weidenaar scored on an error by Garcia at shortstop.OSU finished with five hits in the nightcap, with both Jarrett Higgins and Wes Jones going 2-for-4.The two teams will conclude the series Sunday at 1 p.m.