For a flat long-distance run in Barrie, the Oro-Medonte Rail Trail is a good bet. This gravel multi-use path follows an abandoned CN rail line parallel to the northwest shore of Lake Simcoe, passing through the communities of Shanty Bay, Oro-Medonte and Hawkestone. The trail is inland, so there aren’t water views. The terrain is a combination of woods and farmland. This excellent interactive map has detailed information and pictures. This website by Ken Brown has a wonderfully detailed description of the trail.
The Barrie end of the trail starts at a parking area off Line 1 S Rd. Follow the trail for as long as you like. There’s some lovely surrounding farmland, and some wooded sections. The northern terminus is at West St. in Orillia.
Add-Ons: The Barrie terminus of the trail is 0.5 km from the north end of the North Shore trail, part of our 6.2 km route along Lake Simcoe. In Orillia, there’s nice running along Lake Couchiching.