In-N-Out Sued for Religious Discrimination, Wrongful Termination

In-N-Out is being grilled with a religious discrimination lawsuit ... a former cook says the company treated her differently and ultimately fired her after she asked for a different work schedule due to her Christian beliefs.

According to the suit, obtained by TMZ, Arianna Rodriguez said she had been working as a cook for the burger chain's Long Beach, CA location for nearly 5 years without issues with a schedule that allowed her to attend church on Sundays.

She claims this wasn't an issue until a new manager started in October. She alleges her Sunday availability then became a "recurring source of workplace conflict" and she got her first-ever write-up during this time.

In December, she claims she went to upper-level management, claiming she had concerns about her availability, church attendance, and unfair treatment … but said her concerns were dismissed.

Then on June 24, Arianna claims "an incident occurred involving food" that she thought was "waste under the workplace practice she had observed" … but she says In-N-Out reported her to HR, suspended her, and began investigating the incident.

It's unclear what the incident was, but the cook claims other employees have done something similar and weren't suspended or fired … only received warnings.

According to the lawsuit, she went to HR to complain about the "unequal treatment" but says she was then fired on July 3 for an alleged policy violation.

She's now suing for religious discrimination, wrongful termination, and more. She's asking for unspecified damages, unpaid wages, and to get her job back.