Lainie Kazan had a whole shoplifting routine down before she was caught red-handed, which is why the store was ready at the exit as she allegedly tried to shoplift on Xmas Eve ... sources at the store tell TMZ.
We're told the mom from "My Big Fat Greek Wedding" came into the same Gelson's supermarket where she was arrested for petty theft on Christmas Eve at least a couple times before and stole stuff ... before she eventually got busted.
Gelson's employees told us they saw a pattern with Kazan -- she would fill up her basket and pretend to walk toward the checkout line, but would then make a quick exit out the door as another group of customers was leaving. We're told security footage backs this up.
Workers were ready for her the last time she came in, and notified the folks in loss prevention ... who were waiting to bust her at the exit. We're told they waited for Kazan to get outside before nabbing her.
As we reported ... her cart had about $180 worth of groceries, and we're told it included cleaning supplies (Comet and Pledge), a hot rotisserie chicken, tomatoes, some Jell-O ... and uncured pepperoni.
We reached out to Kazan ... her attorney, Mark Werksman, tells us the store didn't give Lainie a chance to pay for her items before it made moves to get her arrested, calling it a misunderstanding. Werksman also denies Lainie ever stole from Gelson's in the past. He says Gelson's "overreacted and didn't give her a chance to pay."