Can quod mean as soon as? Cf. Apuleius,
Met. et quod ingressui primum fuerit stabulum prandio participabo.
Or is it the direct object: stabulum quod… prandio participabo.
I think it’s until.
Please, better quoting:
Ego tibi solus hîc pro isto credam, et quod ingressui primum fuerit stabulum, prandio participabo. Hæc tibi merces posita est.
quod goes with stabulum. Basically, he’ll have lunch at the first restaurant.
I thought so, however isn’t it a bit weird to say stabulum prandio participabo? Instead of te Prandio participabo in stabulo quod fuerit primum.
The question has been answered, but I also wanted to point out that primum, in combinations such as quam primum or cum primum certainly can be rendered "as soon as possible:
4 ut ~, ubi ~, cum ~, and similar, As soon as; (sim., with present participle).
ut ~ ‥ indalbabat ENN. Ann. 212; illam ut ~ uidi PL. Epid. 600; ut ~ potuit CIC. Ver. 2.48; LIV. 22.26.1; at ~ ‥ Romulus ‥ conpleuit moenia ‥ usque ad Thessalicas ‥ ruinas LUC. 7.437; PLIN. Nat. 28.21; —ubi ~ terram tetigimus PL. Am. 204; ubi ~ magistratum ingressus est SAL. Jug. 43.2; LIV. 10.35.4; FRO. Ver. 2.p.234(138N); —tu uelim cum ~ poteris tua consilia ad me scribas CIC. Att. 5.10.5; LIV. 21.1.4; cum ~ uisum fuerit LARG. 62; 64; —simul ~ magistratu abiit LIV. 6.1.6; —ibi ~ e naui egrediens clamorem militum audit CAES. Civ. 3.106.4.
b quam ~ (with posse), as soon as; (without posse) as soon as possible.
Glare, P. G. W. (Ed.). (2012). Oxford Latin Dictionary (Second Edition, Vol. I & II). Oxford: Oxford University Press.
But with quod, not so much…