Mont-Orford National Park is the mountain escape just northwest of Magog, with forest trails, lakes, lookouts, and a proper change of air from the lakefront. In summer, the best reason to go is hiking; in autumn, the hardwood colour can be superb.
The park is broad, so choose a trail rather than arriving vaguely. Mont Chauve and the Escalier-du-Nord sector are good options if you want views and a real walk without committing to a wilderness day.