This cocktail is not actually named after Scottish folk hero Robert Roy MacGregor, but after a play loosely based on his life story. It was introduced in 1894 at the Waldorf Astoria New York and is essentially a Scotch whisky Manhattan.
2 oz blended scotch
1 oz sweet vermouth
2 dashes Angostura Bitters
Garnish: lemon twist
Prep: Stir/Strain into chilled glass/Garnish