The deadlock was broken at Oakwell with just four minutes on the clock. Bobby Hassell's cross was intended for Jason Scotland, but in trying to clear the danger, Leicester defender Michael Keane only succeeded in sending the ball into his own net.
Winger Hassell then almost turned goalscorer in the 12th minute when he struck a powerful effort on target, but Kasper Schmeichel in the away net was able to thwart his strike.
Schmeichel was then called into action moments later to deny former Chelsea midfielder Jacob Mellis from the edge of the penalty area.
The hosting Tykes continued to dominate, but both Scotland and Stephen Dawson failed to hit the target with just Schmeichel to beat.
Their pressure finally told five minutes before the break. Mellis and Scotland linked to free Chris O'Grady, who managed to get the better of Schmeichel from inside the area.