Steve Cotterill's City - who top League One - face Walsall in Sunday's Football League Trophy final and second-placed Preston were looking to capitalise by closing the gap to eight points.
Joe Garner gave Preston to lead, but Jabo Ibehre's equaliser 11 minutes from time ensured City sit 10 points clear - although Preston have a game in hand.
As a result of that draw, Peterborough United were able to leap above Barnsley and into the play-off places thanks to a 1-0 win at home to Chesterfield.
That achievement highlights a significant improvement for United, who were 15th when Darren Ferguson left his post as manager by mutual consent on February 21.
Milton Keynes Dons and Sheffield United retained their respective places in the top six after victories of their own.
MK Dons claimed the most emphatic win of the day, beating Notts County 4-1, while United ended a run of five without success in a 1-0 triumph over Port Vale.
At the other end of the table, in-form Crawley Town moved out of the relegation zone after beating third-from-bottom Leyton Orient 1-0 - their third win in a row.
Colchester United were the only team in the bottom four to avoid defeat, but they were denied a crucial three points as Gillingham's Doug Loft scored a last-minute equaliser in a 2-2 draw.
Meanwhile, fellow strugglers Crewe Alexandra suffered a 1-0 defeat at home to Oldham Athletic.
Elsewhere, Bradford City allowed a two-goal lead to slip in the final five minutes of their 2-2 draw with Fleetwood Town, Rochdale defeated Scunthorpe United 3-1 and Coventry City were beaten by the same scoreline at home to Doncaster Rovers.
