After passing through McDougall, Waubamik, McKellar, Fairholme and Dunchurch, the highways travels east through Ahmic Harbour, north of Magnetawan, and through to Sundridge.

From that interchange, the highway progresses northwards through the Municipality of McDougall, passing through the communities of Badger's Corners and Waubamik, where it encounters the Bunny Trail, before curving east and weaving around dozens of lakes.

The route travels in a straight line due east for several kilometres, dipping south momentarily then entering the community of Pearcley.

It passes through the community of Strong and continues generally eastward for several kilometres before encountering an interchange with Highway 11 (Exit 276).

[4] The following year shows it realigned along Municipal Drive and Hoddy's Side Road, bypassing north of the town.

[6][7] The highway was realigned for 3.0 km (1.9 mi) east of the Magnetawan River and paved between there and the Nipissing Road in 1962.

[13] These revisions reduced the length of Highway 124 to 76.1 km (47.3 mi) and established a route that would remain unchanged until the early 1990s.

[14] In August 2006, work began on the Sundridge–South River bypass of Highway 11, as part of the four-laning of that route between Huntsville and North Bay.