"Our industry sources inform us that McDonald's U.S. plans to test all-day breakfast - breakfast items for sale throughout the 24-hour day - in one domestic market, with the test set to begin within the next month or two," the firm says in a research note.
Testing all-day breakfast "makes sense," says Janney Capital Markets analyst Mark Kalinowski. Some of the most "craveable" items on the McDonald's menu are the McMuffins and McGriddles, he notes.
But it could also cause major operational problems.
McDonald's stops serving breakfast at 10:30 a.m. in most markets because its grills aren't big enough to handle breakfast and lunch items.
"It comes down to the sheer size of kitchen grills," the company says on its website. "They simply don't have the room for all of our menu options at one time - especially considering we use our grill to prepare many items on our breakfast menu."