The giveaway is in celebration of National Vegetarian Week which runs from May 13-19.
Diners can pick up their free Spicy Veggie Wrap by downloading the McDonald's app, and picking up the meal after 10.30am.
Spicy Veggie Wrap
The burger giant launched the Spicy Veggie Wrap earlier this year. It features a vegetable medley wrapped in a tortilla, with red pesto veggie goujons, red onions, spicy relish, tomato, and lettuce.
While all the ingredients in the wraps are suitable for vegans, McDonald's has marked the items as vegetarian because the tortillas pass through the same toaster as the buns that contain milk - and therefore there's a minor risk of cross-contamination. The items are both certified by The Vegetarian Society.
McDonald's vegan options
"We're really proud to have worked closely with McDonald's for over 10 years and it's great to see their veggie menu developing, especially as McDonald's tell us a third of their customers think it's important to eat more veggie meals," Lynne Elliot, Chief Executive of the Vegetarian Society, said when the wrap was launched in January.
"There's a growing demand for veggie food everywhere and it's fantastic to see McDonald's meeting the needs of their customers. With the new Spicy Veggie Wrap and Veggie Happy Meal carrying our trademark diners can trust their meal is one hundred percent vegetarian."
Diners should check their nearest participating store on the app, as not all McDonald's outlets are included in the promotion.