Tomlin gave the visitors an advantage after 20 minutes when his drive hit the bar and Carl Ikeme on its way into the net.
Bakary Sako and Pennant applied pressure from set pieces for the home side but Peterborough held firm to stay ahead at the interval.
The visitors made Wolves pay for their missed chances to double their advantage in first-half stoppage time through Tommy Rowe.
George Boyd and Dwight Gyale led an incisive Boro breakaway before Rowe slotted home to give Posh a two-goal lead.
Pennant went close for Wolves early in the second half but as the hosts chased the game they went three behind on 70 minutes.
Peterborough were deadly on the break once again as Gayle collected Mark Little's cross to slide home and put the result beyond doubt.