[3] The reserve is located in the unorganized territories of Rivière-Mouchalagane, Rivière-aux-Outardes and Lac-Walker, which are respectively in the Caniapiscau, Manicouagan and Sept-Rivières regional county municipalities.

[1] The Groulx Mountains form a tabular massif consisting of a long high plateau with several slightly convex peaks exceeding 1,000 metres (3,300 ft) elevation.

[3] The rock is visible in outcrops at the top, while the slopes are covered with glacial till deposits up to a few meters thick.

The internal hydrographic network of the reserve is composed of about twenty small lakes and head streams.

Lower down the vegetation is mostly black spruce (Picea mariana) and balsam fir (Abies balsamea), mixed with white spruce (Picea glauca) at about 700 metres (2,300 ft), white birch (Betula papyrifera) and trembling aspen (Populus tremuloides).

There are six animal species on the reserve that benefit from protection status: wolverine (Gulo gulo), boreal woodland caribou (Rangifer tarandus caribou), golden eagle (Aquila chrysaetos), bald eagle (Haliaeetus leucocephalus), rock vole (Microtus chrotorrhinus) and least weasel (Mustela nivalis).

The Monts Groulx are visited annually by about 500 people who come to practice hiking, snowshoeing, telemark skiing and dog sledding.