Opera House was best known for his performances as a five-year-old in 1993, when he won three Group One races, including the King George VI and Queen Elizabeth Stakes and was named European Champion Older Horse.

At Leicester in October he started odds on for an eleven-runner maiden race and pulled clear in the closing stages to win by ten lengths.

Although he was beaten in the Gordon Richards Stakes he looked unlucky in running and did well to finish third behind Dear Doctor (Arlington Million) and Red Bishop (Hong Kong Vase).

[12] Opera House lost his next three starts, beginning with a disappointing sixth place in the Prince of Wales's Stakes at Royal Ascot.

On his debut he traveled to France for the first time for the Prix Ganay at Longchamp, where he led in the straight before being caught close home and narrowly beaten by Vert Amande.

[17] A month later he took the Eclipse Stakes at Sandown, leading in the straight and holding off the late challenge of the Italian champion Misil by a short-head.

Opera House was ridden at Sandown by Michael Kinane as Roberts chose to ride Barathea, who he felt would be better suited by the fast ground.

[20] In the King George at Ascot, Opera House was made 8/1 third favourite in a strong field,[21] behind The Derby winner Commander in Chief and the 1992 European Horse of the Year User Friendly.

Ridden by Michael Roberts, Opera House tracked the leaders before being moved into the lead two furlongs out and stayed on strongly to beat White Muzzle by one and a half lengths with Commander in Chief third.

In the International Classification for 1993, Opera House was rated the best older horse in Europe with a figure of 129, one pound below the three-year-old champion Zafonic.