Jay O’Shea gave the visitors a first-half lead, but Barnsley fought back to force a draw with Winnall equalising just after the hour-mark.
Chesterfield took the lead in the 26th minute. Conor Hourihane stumbled and lost possession and Jimmy Ryan seized on the loose ball before finding O’Shea on the right-hand side of the area and the Irishman fired low into the far corner.
Barnsley had chances to equalise soon after with Winnall having a shot deflected wide and Martin Cranie heading against the crossbar.
The hosts threatened again with Peter Ramage just failing to get on the end of Winnall’s ball into the area and defender Declan John’s follow-up blocked.
Chesterfield survived another major scare when goalkeeper Tommy Lee produced a superb reflex save to keep out home forward George Waring’s shot following a corner.
The equaliser came when Ramage played the ball into the area and Winnall was on hand to finish from close range in the 62nd minute.