Goalkeeper John McCarthy then made a handful of fantastic saves in the shootout as Bale’s side triumphed 3-0 on spot kicks to win the trophy on Saturday.
LAFC had previously broken the deadlock in the 28th minute when a free kick by Kellyn Acosta bounced off the head of Union’s Jack McGlynn and past keeper Andre Blake.
In the second half, Jose Martinez of Philadelphia cut a long-range attack that fell to Daniel Gazdag, who buried it to make the game 1-1.
LAFC went ahead again in the 83rd minute when Jesus Murillo timed his jump perfectly to nod home a corner from Carlos Vela. But the lead was short lived, Philadelphia equalized again for two and a half minutes when Jack Elliott headed past Maxime Crepeau to make it 2-2.
Elliott struck again in the 124th minute to give the visitors their first lead of the game before Bale’s heroism sent the rollercoaster game to penalties four minutes later.
Ilie Sanchez scored the deciding penalty to win the title for LA, which only entered the league in 2018.
At a press conference after joining the club earlier this year, Bale said: “I want to make my mark in this competition, it’s not just for the short term. My goal is to play a big role and try to to win trophies…
“I’m looking forward to playing for the fans and giving them lots of moments to cheer. It’s an incredible club and it became clear that I wanted to be here. Hopefully I can now play my part and win trophies here.”