In this contribution an attempt has been made to shed some light, within the framework of Natural Phonology, on the problem connected with the ‘Classical’ Old English (from now referred to as Old English) vowel system. The undoubtedly true, but somewhat ‘ubiquitously’ sole distinction of the whole vocalic inventory along the long/short symmetry does not appear to have been the only possibility. Here, the focus of attention will be directed to the claim that apart from this obvious quantitative difference, the rather omitted, if not utterly ignored, tense/lax differentiation also seems to have been characteristic of the long/short pairs in the Old English vowel system. For this reason, the model elaborated by Patricia J. Donegan (1985) treating the development of vocalic inventories of various natural languages has been selected as possessing an appreciably powerful explanatory force in accounting for the assumed claim. First, however, some ‘classical’ views on the Old English vowel system will be presented. Then, some data collected from three Early Middle English dialectal areas will be introduced. As generally agreed, the Early Middle English vowel inventories are understood as the next phase in the continuum of the evolvement of the Old English vocalic system(s). What shall reveal of specific importance here will be the fact that it is actually the Early Middle English dialectal vocalic variations that give evidence for the plausibility of the tense/lax distinction already in Old English. Further, it will be noted that Donegan’s framework decidedly fits the observed patterns and emphasises the legitimacy of the suggested claim. Finally, it is intended that this study should, first, ascertain the fact that the Old English vowel system appears to have been characterised by the tense/lax distinction, and second, it should accentuate the significance of Natural Phonology as being a model that accurately explains sound change.