Will Doyle's team took a three-goal lead into half-time on Saturday night in Ferrycarrig Park courtesy of a Claire O’Riordan double and a Kylie Murphy strike.
Wexford put the tie beyond Peamount early in the second half with Emma Hansberry’s strike and O’Riordan competing her hat-trick.
Rianna Jarrett celebrated her first appearance off the bench in almost two years with two goals before Carol Breen rounded off the scoring for the champions.
Shelbourne Ladies were also victorious as they secured a 9-0 victory over Kilkenny United WFC, who made their first WNL trip to Dublin.
Jamie Finn opened the scoring for the Red Pandas with Fiona Donnelly finding the net either side of a Sarah Rowe double to give Shels a 4-0 half-time lead.
A Noelle Murray double along put them further ahead while substitute Sinead Taylor, Avril Beirley and Courtney Higgins also scored for Casey McQuillan side.
Shelbourne will meet Wexford on Sunday, November 8 in the Continental FAI Women's Senior Cup Final at Aviva Stadium in what promises to be a thoroughly entertaining affair.
Elsewhere in the WNL, Galway WFC continued their 100 per cent start to the season with a 5-0 victory over Castlebar Celtic in the Connacht derby on Saturday.
It took until the 48th minute for the deadlock to be broken by Aisling Meaney, who then doubled the lead for Don O'Riordan's side 10 minutes later.
Savannah McCarthy put tie beyond Castlebar before Lynsey McKey found the net twice - the second of which was a last-minute penalty - to see Galway move onto six points.
On Sunday afternoon, UCD Waves collected their first League win of the season with an impressive 5-1 triumph away to Cork City WFC at Bishopstown Stadium.
Julie-Ann Russell opened the scoring for UCD and striker Eleanor Ryan Doyle made it 2-0 when her shot took a deflection off Ciara McNamara and looped into the net.
Aine O’Gorman scored either side of half-time for the visitors before Ciara Desmond pulled one back for Cork, but Emily Cahill headed home the fifth goal for UCD.
Continental Tyres Women's National League Results
Cork City WFC 1-5 UCD Waves
Galway WFC 5-0 Castlebar Celtic
Shelbourne Ladies FC 9-0 Kilkenny United WFC
Wexford Youths WFC 8-0 Peamount United