Bednar's seventh goal in seven games, a stunning strike by Robert Koren and a double from Kevin Phillips - all in the space of 28 second-half minutes - saw off promotion rivals Bristol City, who had won three of their previous four games.
The victory was no more than Albion deserved as they dominated the game for long spells only to be frustrated by their finishing, the woodwork and goalkeeper Adriano Basso.
But on-loan Hearts marksman Bednar was not to be denied and he set Albion on the way in the 47th minute, converting a right-wing cross from Carl Hoefkens.
The win moved Albion level on points with Watford but they took top spot on goal difference.
City spent most of the game trying to keep Albion in check, but still had one excellent chance before Koren grabbed Albion's decisive second.
Lee Johnson found himself unmarked at the near post in the 60th minute only to see Dean Kiely turn away his goalbound drive.
It was a timely intervention by Kiely as Albion sealed their success seven minutes later when the unmarked Koren sent a 25-yard drive fizzing past Basso.
Basso then got involved in a mix-up on the edge of the area with team-mate Jamie McCombe in the 72nd minute and Phillips took the ball away from both of them before sliding his shot into an empty net.
Phillips, making his first start in nine games after knee problems, then increased his season's tally to 13 when he converted a James Morrison cross from close range after 75 minutes.
All City had to show for their efforts was an 85th minute consolation strike from Darren Byfield, who saw his shot bounce over Kiely from the edge of the area.
City, despite making a bright start when Lee Trundle was denied by Kiely, were extremely fortunate to have got to half-time on level terms and with 11 men still on the pitch.
Basso twice denied Zoltan Gera and Phillips from long range before Kiely snuffed out City's best chance of the half with a one-handed save to deny Marvin Elliott after a knockdown from Enoch Showunmi.
That was as good as it got for City and it was one-way traffic after that as far as City were concerned.
Phillips fired into the sidenetting when well placed and then Bednar rattled the post in the 28th minute after a left-wing cross from Morrison.
Phillips flashed a header wide and Basso again thwarted Gera before City central defender Liam Fontaine was lucky not to be dismissed for a 41st minute challenge on Bednar as he closed in on goal.
Basso continued his tussle with Gera with another smart save from the Hungary international, before Bednar saw his shot deflected just wide two minutes before the interval.
But Bednar was not to be denied as he led Albion on their second-half romp.