Colloquialisation, a process by which ‘writing becomes more like speech’, has been identified as a powerful discourse-pragmatic mechanism driving grammatical change in native English varieties. The extent to which colloquialisation is a factor in change in non-native varieties has seldom been explored. This article reports the findings of a corpus-based study of colloquialisation in Philippine English (PhilE), alongside its ‘parent variety’, American English (AmE). Adopting a bottom-up approach, a comprehensive measure was derived to determine the degree to which a text prefers grammatical features typical of speech and disprefers those typical of writing. This measure was then used to compare and contrast texts in a parallel, multi-register corpus of PhilE and AmE sampled for the 1960s and 1990s. Evidence for colloquialisation was found to vary across registers. While Philippine press editorials and American fiction show a clear colloquialising tendency, learned writing does not show remarkable changes irrespective of variety. The evolution of PhilE registers cannot be explained by a simple process involving emulation of AmE. The patterns uncovered reflect the uniqueness of the sociohistorical circumstances in which PhilE has evolved.