Great Barren and Quinan Lakes Nature Reserve is located in the upper reaches of the Tusket River watershed, in the Roseway River Glacial Plain natural landscape. Great Barren and Quinan Lakes Nature Reserve encompasses approximately 355 ha, consisting of both mainland and island parcels. Flowages are not included within the boundary of the designated area.

Ridges within the nature reserve support outstanding examples of mature, Red Oak-dominated forest. The Red Oak is mixed with varying amounts of Yellow Birch, White Pine, Red Maple, Witchhazel, Striped Maple, and Balsam Fir. Eastern portions of the reserve also contain Red Spruce, Large-toothed Aspen, and Eastern Hemlock.

Islands in the nature reserve contain old-growth and mature climax, mixed Acadian forest. The islands support a mosaic of pure groves and mixed forest types of Eastern Hemlock-Red Spruce-Sugar Maple-Yellow Birch and American Beech-White Pine-Balsam Fir-Red Maple. Tree heights reach 30 m and diameters at breast height reach 90 cm. One stand also contains a large population of Canada Yew, a once-common species which has disappeared from much of the province.

Map of Great Barren and Quinan Lakes Nature Reserve