Portugal's 1974 Carnation Revolution, that put an end to over 40 years of a Catholic para-fascist corporativist dictatorship. It was ran by insurgents in the Portuguese Army but these never used their guns. The State's Secret Police eventually fired over about 5 people but ended up surrendering without exchanging fire with the armed forces.

On the Carnation Revolution and its significance as a bloodless European revolution, Tony Judt, Postwar (even if only covering the surface). All other substantial literature on the revolution that I know of is in Portuguese.

1989 Velvet revolution in Czechoslovakia that brought about the collapse of the communist regime did not result in any loss of life. Also, the 1993 dissolution of Czechoslovakia, aka the "Velvet Divorce", and the creation of the successor states of the Czech Rep. and Slovakia was entirely peaceful.