This paper intends to provide an Optimality-theoretic analysis of word-stress learnability among Moroccan learners of English. Language acquisition, from an Optimality Theory perspective, is a process of reordering the constraints from an initial state of the grammar to the language-specific ranking of the target grammar. To account for stress development, this paper makes use of Constraint Demotion Algorithm (Tesar & Smolensky, 1996; 2000) which learners adopt to infer the correct hierarchy of constraints. Starting with a default hierarchy supplied by Universal Grammar, learners proceed with recursive demotion of higher-ranked constraints until the correct ranking is reached. The algorithm, starting by initializing the hierarchy, assumes that constraints are unranked, and thus hosted in the same stratum. Sixty Moroccan learners, who have some basic background in linguistics, participated in the study. The informants are third-year students at university. They were administered an oral multiple-choice test that elicited their intuition about English stress pattern. The overall findings of the study reveal that learners' prior (L1) ranking (ALIGNHD-R >> WSP >>NONFIN >> FT-TYPE[subscript IAMB]>>Ft-BIN>> PARSE-[sigma] >> Ft-TYPE[subscript TROC]) influences their learnability of English stress. That is, Moroccan learners misplace stress in English words due to the initial state of their grammar. What follows shows the constraints demotion learners go through to reach the optimized stress pattern of English: (1) Initial stratum = {Ft-TYPETROC} >>; (2) Stratum 1 ={NONFIN} >>; (3) Stratum 2={WSP} >>; (4) Stratum 3 ={FT-BIN, ALIGNHD-R} >>; (5) Stratum 4 ={PARSE-[sigma]} >>; and (6) Stratum 5 ={FT-TYPE[subscript IAMB]}.