Yes, but actually no. I was wrong – they did stop using the tallow in 1990 or so, but that changed the taste and caused their stock value to plummet. They quietly added “natural beef flavoring” back into the ingredients to mimic the original taste, and didn’t bother announcing that the fries were no longer vegetarian (again).

Random web search result:

https://www.thedailymeal.com/1020277/the-mcdonalds-fries-scandal-youve-forgotten-about/

In another misstep, the company demurred from publicly announcing the ingredient change. The discovery left vegans and vegetarians outraged, along with those who came from religious backgrounds like Hinduism which forbade the consumption of beef tallow. Three later sued McDonald’s in 2001 for misleading them. As the Wall Street Journal reported at the time, McDonald’s countered that they never said their fries were vegetarian. Either way, they eventually settled with a $10 million donation to religious and vegetarian groups and an apology from the fast food giant. Nowadays, if you check their “World Famous Fries” webpage, you’ll see “Natural Beef Flavor” clearly listed in their “allergen information” section.

McDonald’s fries ingredients list:

https://www.mcdonalds.com/us/en-us/product/small-french-fries.html#accordion-c921f9207b-item-283bee7dbd

French Fries

Ingredients: Potatoes, Vegetable Oil (canola Oil, Corn Oil, Soybean Oil, Hydrogenated Soybean Oil, Natural Beef Flavor [wheat And Milk Derivatives]*), Dextrose, Sodium Acid Pyrophosphate (maintain Color), Salt. *natural Beef Flavor Contains Hydrolyzed Wheat And Hydrolyzed Milk As Starting Ingredients.

Contains: Wheat, Milk.

Here’s an archive of the (paywalled) WSJ article referenced in the first link:
https://archive.is/55Zys