Albion had picked up just one point from their previous three games to slide from the top of the table to fourth.
But substitute Zoltan Gera put them on course for only their second win in seven league games when he pounced on the stroke of half-time.
Ishmael Miller doubled their advantage in the 59th minute before Bednar, whose first Albion goals were at Plymouth in December, bundled home his 16th of the season after 67 minutes.
Plymouth had arrived at The Hawthorns on the back of four successive wins that had catapulted them into the thick of the promotion race.
But they lacked the firepower that Albion have at their disposal and that was the key difference between the sides.
Gera, axed after an ineffective display in the previous game against Hull City, found himself thrown back into the action after 17 minutes when Filipe Teixeira was forced off when he fell awkwardly.
It proved to be a stroke of luck for Albion as Gera made their greater possession finally pay-off in first-half stoppage time thanks to good work by Bednar.
Bednar's powerful run into the area saw him pick out Miller, who had wasted a good chance to break the deadlock in the 20th minute when he dragged his shot wide.
This time he was on target but his effort was parried by Plymouth goalkeeper Luke McCormick.
Unfortunately for Plymouth, the rebound flew straight to Gera, who stabbed home his eight goal of the season from six yards.
Albion's advantage should have been short-lived as Plymouth had an excellent chance to equalise on the stroke of half-time.
Gary Teale's inswinging corner was met by Lilian Nalis, but his powerful header flew just the wrong side of the post.
Peter Halmosi then had a close-range shot blocked before Albion secured their success with two goals in an eight minute second-half spell.
Miller, who had seconds earlier been denied by a smart save from McCormick, pounced on a loose ball on the edge of the area and let fly with an hopeful overhead kick.
The former Manchester City marksman looked almost embarrassed as the ball looped over the stranded McCormick and into the net.
Bednar then set the seal on the win with a predatory piece of finishing.
Jonathan Greening whipped in a left wing cross and Gera nodded the ball back into the path of Bednar, who easily beat McCormick from close range.