Based in Melbourne's north-west, Avondale were in the lowly sixth tier of Victorian football in 2009 but won promotion five times over the next six seasons to reach the NPL, the state's top league.
They have now made their mark on the national stage at their very first attempt - against one of Australia's most illustrious clubs in Marconi, four-time champions of the National Soccer League.
Goals from Kane Sheppard, Joey Katebian, Liam Boland and Evan Christodoulou did the damage for the 'Avengers' in Wednesday night's round of 32 clash at ABD Stadium in Broadmeadows.
Sheppard opened the scoring in just the second minute with a brilliant piece of individual skill, turning Marconi's defence inside out to give Avondale a dream start.
But the visitors responded just a few minutes later with another stunning goal as James Andrews bamboozled three defenders with a stuttering run along the edge of the penalty area, before unleashing a curling shot that snuck inside the right post.
Marconi had the better of the play for the rest of the first half but couldn't capitalise, and were made to pay in the 54th minute when former Brisbane Roar striker Katebian put Avondale back in front.
Boland added another from the penalty spot in the 72nd minute after he was needlessly brought down by goalkeeper Nenad Vekic before Christodoulou sealed the deal in the dying minutes.
Elsewhere on the tournament's opening night, Lions FC held off a ferocious comeback from NPL Queensland rivals Olympic to win 3-2 in Brisbane.
Olympic were 2-0 down early in the first half but drew level with nine minutes to go - only for substitute Carter Glockner to restore Lions' advantage three minutes from time.
Newcastle-based Broadmeadow Magic enjoyed a 4-1 win over a 10-man Canberra FC in the capital, while APIA Leichhardt Tigers also tasted victory on the road with a 1-0 result at the Port Melbourne Sharks.
A-League teams begin play in the FFA Cup next week.