All-day breakfast at McDonald’s is an apparent success. According to an internal company memo obtained by the Wall Street Journal, McDonald’s operators are being advised to prepare for a nationwide extension of the all-day breakfast platform as early as October.

McDonald’s began testing the expanded morning meal past 10:30 a.m. in April at 94 San Diego stores. Even limiting the all-day menu to just nine items—Egg McMuffin, Sausage McMuffin with Egg, Sausage Burrito, Sausage McMuffin, Hash Browns, Hotcakes, Hotcakes and Sausage, Fruit & Maple Oatmeal and Fruit ‘N Yogurt Parfait—some operators and industry analysts questioned whether this would disrupt kitchen operations. If it did, those problems either were overcome or the chain has decided to move ahead and remedy them in time for the rollout.

Last month, the test was expanded to a dozen locations in Greenville and Greenwood, Miss., and then 132 restaurants in Nashville, where biscuits have been prepared all day.

How important could a successful nationwide all-day breakfast launch be for McDonald’s? That will be more clear tomorrow when the company announces Q2 earnings and June sales.