too many cooks spoil the broth

There is the proverb, the more cooks the worse potage.
[1575 ?J. Hooker Life of Carew (1857) 33]

When‥an undertaking hath been committed to many, it caused but confusion, and therefore it is a saying‥Too many Cooks spoils the Broth.
[1662 B. Gerbier Principles of Building 24]

She professes to keep her own counsel. ‥‘Too many Cooks spoil the Broth.’
[c 1805 J. Austen Watsons (1972) VI. 318]

As Amyas sagely remarked, ‘Too many cooks spoil the broth, and half-a-dozen gentlemen aboard one ship are as bad as two kings of Brentford.’
[1855 C. Kingsley Westward Ho! II. vii.]

It was a great mistake to think that administration was improved by taking on more administrators. ‥‘Too many cooks spoil the broth.’
[1979 Guardian 7 Nov. 6]

Too many cooks spoil the broth and at Apple there is now the equivalent of Marco Pierre White, Anton Mosimann and Nico Ladenis.
[1997 Times 8 Aug. 25]

Related to: assistance; busybodies; work

Bibliography of major proverb collections and works cited from modern editions is available here.

Too many persons involved in managing an activity can ruin it, as in Without a conductor, every player had an idea for how the music should go--too many cooks spoil the broth. This expression alludes to each of many cooks adding something to a soup, which finally tastes awful. It was already considered a proverb in 1575 (by George Gascoigne in The Life of P. Care).