Habitual aspect in Palenquero, an Afro-Hispanic creole spoken in San Basilio de Palenque, Colombia, has been described as being expressed by the preverbal marker asé (e.g., Schwegler 1992:224, Schwegler & Morton 2003). The current study analyzes the variable use of asé using the variationist method (Labov 1966) to uncover distributional patterns and typological insights from grammaticalization theory (e.g., Bybee et al. 1994) to account for those patterns. Two variable contexts are defined: first, the broad domain of present temporal reference, and second, in the subcontext of dynamic verbs, co-occurring asé vs. zero. The data were taken from transcriptions of sociolinguistic interviews and conversations with 18 speakers recorded during July, 2010 and May, 2011 in San Basilio de Palenque. Systematic quantitative analysis confirms that tense-aspect marking in Palenquero is characterized by form-function asymmetry, with habitual equally expressed by both asé and 'zero'. It was found, however, that asé is favored in frequentative (more than in habitual) aspectual contexts and in affirmative (more than negative) contexts; it never appears in progressive contexts, and is disfavored with the main verb asé 'hacer'. All of these findings are consistent with predictions made in a grammaticalization framework (Bybee et al. 1994, Givón 1979). This study contributes to both creole studies and variationist studies, in that it brings accountable quantitative methods to bear on long-standing issues surrounding creole grammars.