Wycombe moved into the second round of the Worthington Cup but only after a dramatic 88th minute equaliser from recent signing Stewart Castledine had brought the aggregate scores level at 3-3 on 90 minutes.
Wycombe striker Jermaine McSporran had brought the tie level on 20 minutes after fine creative work from Wycombe's man of the match Dannie Bulman.
McSporran controlled the ball before racing past visiting keeper Lee Harrison and drilling his angled drive into the unguarded net.
But within just three minutes Barnet were again ahead on aggregate, 26-year-old striker Tony Richards controlling the ball 35 yards out before lifting a glorious lob over the stunned Wycombe keeper Martin Taylor.
Harrison's brilliance throughout the first period kept the score down, McSporran suffering from a tremendous blocking save on four minutes.
On 34 minutes the 29-year-old former Barnet player of the year exploded into action to tip away Wycombe sub Jason Cousins' effort, then on 38 he produced a fabulous point blank save from home striker Andrew Baird.
Despite Wycombe's efforts to level Barnet sub Ben Strevens came close to adding to the scoreline, efforts on 73 and 87 minutes both flashing inches wide of the Wycombe woodwork.
But with time running out Castledine struck crashing home from close range after fine work from Danny Sender.
Wycombe finally broke Barnet's hearts when going ahead for the first time in the tie on 105 minutes, centre back Paul McCarthy
flicking Michael Simpson's cross over the surprised Harrison.