The visitors had the better of the early stages of the contest, coming close to making the breakthrough inside the opening 10 minutes when Tim Ream managed to get in a header on goal, only for David Forde to palm it away.
Matt Mills was the next Wanderers player to force the Irish stopper into action, once more rising highest to get his head on the ball, which this time was straight at Forde between the sticks.
Having absorbed much of the pressure, Millwall managed to muster their own opening shortly before the half-hour mark when Magaye Gueye's pass was latched on to by Lee Gregory, but he was unable to get his shot on goal.
Both sides continued to press for an equaliser as the first half drew to a close, with Darren Pratley in particular culpable for missing a good opportunity when hesitating before eventually scuffing his shot, while Rob Hall's appeals for a penalty were quickly waved away moments later.
Ian Holloway's charges came close to grabbing a valuable lead heading into the interval when an unmarked Angel struck the ball on the half-volley, although he could not keep his attempt on target as the half ended all square.