Green’s Dictionary of Slang

take the biscuit v.

also cop the biscuit, sneak..., win..., take the bakery, take the cookie, take the rusk
[the fig. ‘sweetness’ or ‘tastiness’ of the biscuit; var. on take the cake v. (1)]

to beat all rivals, esp. with the implication that the person, announcement, event etc. is even more startling or appalling than might have been expected.

[US]Lantern (N.O.) 20 Oct. 3: For keeping away from trouble a peeler takes the cookie.
[UK]Sporting Times 3 May 5/4: That extremely Catholic list of smart social functions, ‘To-day’s Arrangements,’ fairly won the biscuit on Thursday last.
[UK] ‘’Arry in ’Arrygate’ (Second Letter) in Punch 15 Oct. 169/3: I know ’Arrygate girls cop the biscuit for beauty.
[UK]Sporting Times 9 Apr. 1/3: The Strong Man, who [...] bursts into tears and faints in the dock, takes the bun, the biscuit, the rusk and the entire bakery.
[UK]G.B. Shaw John Bull’s Other Island Act III: You tike the biscuit at thet, you do.
[Aus]Sydney Sportsman (Surry Hills, NSW) 10 Aug. 3/2: [F]or such an offence ‘Ernest Knight’s English Dramatic Company’ [...] took the whole bakery.
[UK]Wodehouse Psmith in the City (1993) 35: At the hard-headed, common-sense business you sneak the biscuit every time with ridiculous ease.
[Ire]Joyce ‘Two Gallants’ Dubliners (1956) 49: ‘Of all the good ones ever I heard,’ he said, ‘that emphatically takes the biscuit.’.
[Ire]Joyce Ulysses 312: Twenty to one, says Lenehan. Such is life in an outhouse. Throwaway, says he. Takes the biscuit and talking about bunions.
[US]W. Winchell On Broadway 5 July [synd. col.] Look takes the cookie for obvious caption-writing.
[UK]A. Sinclair My Friend Judas (1963) 39: Beelzebub, you take the biscuit.
[UK]Wodehouse Much Obliged, Jeeves 42: Of all the soppy families introduced to his notice the Bassetts took the biscuit.
[UK]T. Paulin ‘The Bungalow on the Unapproved Road’ in Fivemiletown 1: The headboard was padded / with black vinyl – / just the ugliest thing / I’d seen in a long time, / though the new wallpaper / they’d bought in Wellworths – / tequila sunsets / on the Costa Brava – / might take the biscuit.
[UK]C. Dexter Daughters of Cain (1995) 38: She just about takes the biscuit, that woman – give or take one or two congenitally compulsive liars we’ve had in the past.
[UK]J. Hawes Dead Long Enough 262: You Brits take the sheer shagging biscuit.
[UK]Observer Rev. 21 Aug. 7: I am thoroughly sick of lists, but this one takes the biscuit.
[UK]Times 30 Apr. 18/1: For timing, though, Anne and Mark take the biscuit.