This paper analyzes optional glottal stop deletion in Standard Arabic. This deletion is typically accompanied by lengthening or gliding of an adjacent vowel, and deletion can be blocked when this lengthening/gliding is not possible, and also when deletion would create homophony. This paper assesses the ability of various OT-based theories of optionality to account for glottal stop deletion, arguing that the rank-ordered model of EVAL (ROE; Coetzee 2006) provides a better account than alternatives such as partially ordered grammars (PO; Anttila 1997, 2007) and serial variation (SV; Kimper 2011).