The first certain chief of the Clan Gregor was Gregor of the Golden Bridles. His son, Iain Camm, One-Eye, succeeded as the second chief before 1390.

King Robert the Bruce gave the barony of Loch Awe to the Campbells for their aid in raising him to the throne. Locha Awe was MacGregor land and the Bruce left it up to the Campbells how they would take possession of this area. The Campbells built the castle of Kilchurn and the MacGregors were forced to retreat deeper into their lands until they were eventually restricted to Glenstrae.

Iain the Black died in 1519 without a male heir. The Campbells supported Eian MacGregor as chief since he was married to the daughter of Sir Colin Campbell of Glenorchy. Eian's son, Alistair, fought the English at Pinkie Cleugh but died shortly after. In 1560 Gregor Roy MacGregor fought the Campbells as an outlaw after Sir Colin Campbell of Glenorchy refused to recognise his claim to his estates. In 1570 he was captured and killed by the Campbells. His son, Alistair, took over as chief but was unable to stop the Campbell persecution of the MacGregors.

A Royal forrester, John Drummond, was murdered by after hanging a band of MacGregors for poaching. The King then issued an edict aboloshing the name MacGregor. What this essentially meant was that MacGregors had to renounce their name or suffer death. The chief and 11 of his chieftaines were hanged in Edinburgh. The rest of the Clan scattered many taking other Highland names to conceal their lineage and thus avoid being hunted like animals.

Despite this treatment 200 men the Clan fought against Cromwell during the civil war. In gratitude King Charles II repealed the proscription on the name MacGregor but it was re-imposed when William of Orange took the throne.

This is the time of the legendary Rob Roy MacGregor. Born in 1671 he had to assume his mother's name of Campbell. He fought on the Jacobite side at the Battle of Sheriffmuir but after the battle he began a life of plundering and was a thorn in the side of the government until his death in 1734.

The proscription was again repealled, this time for good, in 1774. At this time there were 826 MacGregors who wanted to claim the chiefship but it was finally awared to General John Murray and descendant of Duncan MacGregor of Ardchoille who died in 1552.