This paper introduces serial Harmonic Grammar, a version of Optimality Theory (OT; Prince and Smolensky 1993/2004) that reverses two of Prince and Smolensky’s basic architectural decisions. One is their choice of constraint ranking over the numerically weighted constraints of its predecessor, Harmonic Grammar (HG; Legendre, Miyata and Smolensky 1990; see Smolensky and Legendre 2006 and Pater 2009 for overviews of subsequent work). The other is their choice of parallel evaluation over a version of OT in which the representation is changed and evaluated iteratively (Harmonic Serialism; Prince and Smolensky 1993/2004: ch. 2, McCarthy 2007 et seq.). I introduce serial HG with an analysis of syllabification in Imdlawn Tashlhiyt Berber (Dell and Elmedlaoui 1985, 1988, 2002), the same case that Prince and Smolensky use to introduce OT. This analysis illustrates advantages of both serialism and weighted constraints. I also discuss some of the positive consequences of the adoption of serialism for the typological predictions of HG, as well as some outstanding issues for further research on serial versions of both OT and HG.