Hi, I live in Glengarry, so I can tell you that at the time you are talkimg about, the parish, which was vast, was known as Kilmonivaig. Glenquoich was a small area in the subdivision of Glenelg, which was all part of the Glengarry Estate belonging to the Macdonell clan. Glenquoich was used for summer grazing for the cattle but few people ever lived there all year even when it was turned into one of the early sheep farms in the late 1700s. Later, in the 1800s, it was developed as a sporting estate by the Ellice family and their long-term tenant, Lord Burton. It was later flooded to make a hydro-electric dam (in the 1950s). There are still, only a handful of people living there. It is stunning, mountainous scenery now used mainly by walkers, climbers and (a few) sportsmen. Several thousand of the local people emigrated from the glen during the clearances in the late 1700sand early 1800s. Most went to Canada - to Glengarry County in Ontario.
I work in the local Heritage Centre, so I would be interested in any other info you have about this ancestor.
All the best, Stroma
I should have added that the boundary of Glenquoich is at the head of Loch Hourn - a large fjorg type inlet on the west coast.