We examined the reliability, validity, and responsiveness of the Neonatal Oral-Motor Assessment Scale (NOMAS) in healthy preterm infants. Feeding records of 147 infants (71 males, 76 females; gestational age [GA] ≤ 36wks), taken from the day bottle-feeding was initiated to the day the infants were discharged, were used to examine the psychometric properties of the normal and disorganized categories of the NOMAS. The infants, with or without experience of breastfeeding, were all fed by bottle, with either formula and/or breast milk. GA ranged from 24 to 35.9 weeks (mean 29.7wks, SD 2.7) and birthweight ranged from 470g to 2570g (mean 1251.1g, SD 425.9). Postmenstrual age (PMA) at the starting point of bottle-feeding ranged from 29.4 to 40.1 weeks (mean 33.8wks, SD 1.7). We found that the NOMAS had satisfactory internal consistency (Cronbach's α >0.70) in the normal category for 32 to 35 weeks’PMA. Moderate correlations were found between scores on the NOMAS and feeding performance for all age groups except for PMA of ≥ 36 weeks (absolute Spearman's rs=0.51-0.69), indicating acceptable convergent validity. The NOMAS demonstrated moderate responsiveness to changes in oral-motor skills in every 2-week period, ranging from 32 to 36 weeks’PMA (standard response mean greater than 0.5). This study demonstrated that the normal and disorganized categories of the NOMAS are useful, with acceptable psychometric properties, in assessing oral-motor function in preterm infants aged 32 to 35 weeks’PMA. Future research on infants with abnormal oral-motor skills is needed to further validate psychometric properties of the dysfunction category of the NOMAS.