The chain plans to test all-day breakfast in the San Diego area starting next month, the company confirmed to CNBC.
"We look forward to learning from this test, and it's premature to speculate on any outcomes," wrote spokeswoman Terri Hickey in an email. "We're excited to serve our customers in this area some of McDonald's great-tasting breakfast sandwiches, hash browns and other favorites all day long."
Big chains such as McDonald's usually test an item in a limited number of locations to work out the kinks before deciding whether to roll out it nationally.
Typically, locations stop serving breakfast after 10:30 a.m. local time during the week and as late as 11 a.m. on the weekends.
Testing 24/7 breakfast "makes sense" to Janney analysts, who note, "We believe customers generally want to see McDonald's offer breakfast items all day."
In the past, McDonald's has stressed how limited grill space hampers its ability to serve all-day breakfast.
McDonald's plan to test 24/7 breakfast comes amid increased pressure in morning sales from Taco Bell's breakfast menu, which launched last year. As part of its domestic turnaround effort, McDonald's has doubled down on breakfast as a key focus for growth through coffee promotions and its emphasis on cooking with eggs it cracks in the kitchen.