This paper proposes an alternative analysis for mid vowel alternations in verbal stems in BP, treating them as vowel coalescence, where two input vowels unite into a single output vowel that shares features of its ancestor, in the framework of Optimality Theory (Prince & Smolensky, 1993; McCarthy & Prince, 1995). The vowel coalescence in BP is triggered by the markedness constraint ONSET, which prohibits vowel initial syllables, competing with faithfulness constraints. The ranking of MAX and the markedness constraint ONSET above UNIFORMITY (no coalescence) yields coalescence instead of deletion. For vowel neutralization in BP, I assume the typology of height contrasts in relation to stress proposed by Beckman (1997) and McCarthy (1999); this typology needs to be adapted for Portuguese, since Portuguese has a seven vowel system. In addition, the faithfulness constraint IDENT-SUFFIX is introduced to explain leftward coalescence since coalescence in BP does not occur in locally adjacent segments.