This paper addresses the early variation in what has been called the [prep_que] variable in Spanish nominal complement clauses, i.e. the alternation between de que and que in examples such as enseñal (de) quelo estimo, Zulema, este anillo ofrezco (CORDE) ‘as a sign that I appreciate You, Zulema, I offer this ring’. By applying several subsequent quantitative analyses on corpus instances of the sequences N de que and N que, the locus of variation is restricted to such an extent that the variation can largely be accounted for. A collostructional analysis identifies 31 central nouns of the N de que complement clause construction. A diachronic cluster analysis delimits the temporal dimension of the variation to the 16th and 17th centuries. A distinctive collexeme analysis identifies nine nouns which are used in both constructional formats to a comparable degree: causa ‘cause’, duda ‘doubt’, esperanza ‘hope’, fe ‘faith’, opinión ‘opinion’, recelo ‘fear’, señal ‘sign(al)’, sospecha ‘suspicion’, and temor ‘fear’. Detailed contextual analysis of the use of these nine nouns by means of a mixed-effects logistic regression reveals that the use of the nouns with a determiner is correlated with the de que variant, and the use of the nouns as part of complex predicates, as in tener sospecha ‘have suspicion’, is associated with the que variant of the complement clause.