In Montcalm County, M-66 intersects M-57 in a rural area south of Sheridan before running north on Sheridan Road through Stanton. The highway jogs west along Main Street in Stanton before returning to a northerly course on a discontinuous section of Sheridan Road. The roadway curves around the west end of Hemmingway Lake near Cannonsville Road. West of Edmore, M-66 turns northwesterly along M-46 on Edmore–Howard City Road to Six Lakes. M-66 separates there and returns to its northerly journey along Six Lakes Road between Little Bass Lake and First Lake. The road crosses into Mecosta County as 30th Avenue north of Six Lakes. The highway intersects M-20 at the intersection with 9 Mile Road in Remus. This area of rural Mecosta County is more heavily forested with rolling hills and sporadic farms. In Barryton, the roadway crosses the Chippewa River. M-66 continues north passing Merrill Lake before crossing into rural eastern Osceola County at Mesceola Road.