Albion squandered early chances but never looked like losing their grip after getting in front. They could have been two up inside ten minutes only for openings cleverly created by Richard Chaplow to be wasted when Craig Beattie fired high and wide, before Ellington failed to get the ball past home goalkeeper Shwan Jalal at close range.
Released by Aaron McLean, Josh Low almost made Albion pay with a low drive into the side netting and Albion keeper Dean Kiely also had to go full stretch to his right to bundle away a sweetly taken free-kick by Jamie Day.
Within a couple of minutes Day was clearing a Beattie effort off the Posh goal line to concede a 32nd minute corner, which was swept over by Neil Clement for Gera to meet running in at the far post and force into the roof of the net with an unstoppable header.
Albion doubled their advantage on the stroke of half-time with Gera again involved. The Hungarian's drive was parried by Jalal and bobbled in the area before being swept into the net by Ellington.
Posh began the second period with a spirited burst that saw Kiely twice in action to flick away a Shane Blackett header with Charlie Lee reaching the ball first, but blazing over the bar. Lee almost went one better with a header from a Day cross that Kiely did well to reach.
McLean burst forward to blast a shot just wrong side of Keily's left-hand post, but Albion's Martin Albrechtsen and skipper Jonathan Greening never relaxed their grip in the second half and McLean increasingly become a solitary challenger.