In this paper we investigate the cues governing stress perception in Spanish - an issue that has been subject to debate and remains largely unresolved. While there is general agreement as to the ability of Spanish listeners to detect and reliably produce stress contrasts, there is some disagreement on the roles played by individual stress cues. In this study, we focus on early stress processing in a passive oddball paradigm aimed at eliciting a mismatch negativity response to changes in stress. Individual features (spectral tilt and f0) rather than feature bundles are used to induce stress shift. A vowel change is used as a control condition. The results show that while both spectral tilt and f0 manipulations result in mismatch negativity, the latter evokes a stronger response that equals the effect of a change in the quality of the stressed vowel. The results are in line with previous studies on stress correlates in other languages, pointing to a possible cross-linguistic pattern.