Using a large corpus of transcribed audio-recordings, we analyse patterns of intra-individual variation (IAV) in Upper-German dialects (mostly High Alemannic, Swabian, and East Franconian). We take a closer look at two grammatical domains that are particularly informative with regard to the syntax-morphology interface: (i) the system of case-marking distinctions; (ii) the substitute infinitive construction (i.e. IPP, “infinitivus pro participio”) plus word order variation in the verbal complex. These phenomena suggest a form of non-conditioned IAV, meaning that no obvious (grammatical) conditioning factors can be identified. Nevertheless, the variants are not chosen arbitrarily: there are co-occurrence restrictions of certain variants, and variability always draws from the typological space of attested grammatical systems. In this chapter we take a constraint-based perspective on this type of IAV and show its high degree of variability can be modelled using Stochastic Optimality Theory (StOT). In doing so, we address the special properties of data from spoken language corpora, both with regard to theoretical modelling and the possibilities of an IAVanalysis.