In the age of the on-demand economy, sooner or later everything is just a few taps of a smartphone app away. Even burritos.

Chipotle Mexican Grill, the popular chain known for its “fast-casual” burritos, said this week it has begun offering food delivery through Postmates, a San Francisco-based delivery start-up that is growing quickly.

Under the arrangement, Chipotle delivery is now available in 67 cities in the United States where Postmates operates. The cost of delivery, which is based on distance, will start at $4.99 and go as high as $7.99 per order, according to a Postmates spokeswoman.

The deal, which Chipotle announced in a conference call with investors earlier this week, is a coup for Postmates. The start-up — which has a fleet of more than 10,000 couriers to deliver food, groceries, office supplies and other goods for users who have the Postmates app — has fought aggressively to expand into new cities since it was founded three years ago, while competitors like GrubHub and Yelp have sought to bolster their own delivery offerings. Signing large partners like Chipotle, as well as recently inking a deal with Starbucks, will likely raise Postmates’s visibility.

The deal brings a different pricing model for Postmates. Typically, consumers pay it a delivery fee that varies based on the distance traveled by a courier; in the Chipotle deal, the pricing is capped. That should eliminate excessively high fees for consumers, though outlets like Re/code have questioned whether that is really the case.

The deal could also be a boon for Chipotle. To date, the chain has not provided an official delivery service, even though people could order Chipotle meals through delivery apps like Postmates or other start-ups like Doordash.

Mark Crumpacker, Chipotle’s chief marketing and development officer, said the company has seen 30 percent month-over-month growth in delivery orders since Postmates first began delivering Chipotle. That helped spur the chain to hammer out the details of what its delivery experience should look like.

“There have been a lot of people that have been delivering Chipotle through various services over the years and we’ve tried in a lot of cases to shut them down,” Mr. Crumpacker said on the call. “We weren’t sure whether the quality was going to be sufficient or whether they were following our rules.”

Recently, Chipotle has also been grappling with a problem in its pork supply that caused some of its more than 1,800 stores to run short of carnitas.