The hosts had taken the lead on a pudding of a pitch when Alfie Mawson struggled to clear from a boggy six-yard box and Danny Mayor slid in to score, but Onyedinma showed his clinical touch with a classy finish midway through the second half.
The game looked to be in serious doubt once the players arrived at the stadium at 1.30pm, when a layer of snow and sleet had made the pitch incredibly sludgy with the ball getting stuck in muddy puddles in several areas.
However, referee David Webb allowed the match to go ahead and so the Blues started with just one enforced change from the 1-0 victory over York the previous week, with Matt Bloomfield taking the place of the departed Josh Scowen.
Direct football was always going to be the order of the day and the Shakers came close inside the third minute when Aaron Pierre headed off the line from Ryan Lowe’s effort after the Blues struggled to clear the ball from a corner.
Lowe had another sight of goal on the quarter-hour mark but blasted over after good work from Craig Jones down the right, while Wanderers were struggling to create at the other end, although Aaron Holloway and Fred Onyedinma looked likely to test the keeper at least before the treacherous conditions prevented them from getting their shot away following Joe Jacobson’s corner.
Inevitably, the sodden pitch would lead to a goal and it came for the Shakers on 30 minutes when a low cross from the right got stuck between Alfie Mawson’s feet inside the six-yard box, allowing Danny Mayor to slide in and turn the ball home.
Wycombe responded well and saw Aaron Holloway’s shot blocked en route to goal after Nick Pope had punched unconvincingly at a corner, and Aaron Pierre curled wide from the edge of the box after Sam Wood returned a corner into the danger zone.
The half ended with the Blues well on top, and manager Gareth Ainsworth will have been heartened by how his side had adapted well to the conditions after a sticky start.
Wanderers were nearly level when Aaron Holloway’s header was just about fumbled behind for a corner at the near post, before the game developed into a frantic end-to-end encounter with both sides looking capable of finding the net.
Marcus Bean surged from deep into the box on the hour-mark and claimed for a penalty as the ball was nicked off him and out for a corner, but it was the hosts who were aggrieved when the Wanderers’ equaliser did come.
Joe Jacobson whipped in a ball from the left and Fred Onyedinma muscled his man out of the way before crashing home an unstoppable drive with his left foot, although Bury felt he had either used his hand or shoved his man in the process.
The striker almost had a second when Pope rushed out to foil him three minutes later, and the keeper was called upon again to get behind Aaron Pierre’s well-hit strike following a corner.
As the game neared stoppage time, Danny Rose wasn’t far away with a volley from a cross from the right, and neither side could find a winner on a day when a point can never be considered a bad result given the conditions.
Wycombe: Ingram, Jombati, Jacobson, Mawson, Pierre, Murphy, Bloomfield, Bean, Wood, Onyedinma, Holloway.
Unused subs: Richardson, Rowe, Senior, McClure, Hayes, Craig, Ephraim.
Bury: Pope, Jones, Hussey, El-Abd, Cameron, Soares, Tutte, Etuhu, Mayor (Nardiello 53), Lowe (Rose 31), Hope (Adams 78).
Unused subs: Lainton, McNulty, Sedgwick, Burgess.
Attendance: 2,932 (270 from Wycombe)