Children diagnosed with autism spectrum disorder (ASD) that regress in skills show more significant deficits in social communication and show intellectual disability relative to children with ASD without a regression. As early as 12 months, peak alpha frequency (PAF) differences have been observed in infants prior to an ASD diagnosis. We measured peak alpha band frequency (6-12 Hz) brain activity using EEG under a task-free condition at 9 and 12 months. Developmental abilities were assessed using the Mullen Scales of Early Learning at 12 and 18 months. Outcome group was determined at 36 months. We examined changes in early development skills in infants with and without familial risk for ASD and the potential role of differences in PAF in explaining these changes. We hypothesize PAF in the first year of life would be related to changes in developmental abilities in the second year within and across diagnostic outcome groups. Preliminary results showed that gross and fine motor, receptive and expressive language, and visual receptive skills increased between 12 and 18 months, with outcome group differences observed in all areas except gross motor. However, the degree of change overtime for receptive and expressive language, and visual receptive skills differed by outcome group. Additionally, PAF increased with age in the frontal, central, and occipital regions. PAF differed by outcome group across all regions, except for the frontal. Next, we will examine the relationship between PAF in the first year of life and change in developmental abilities in the second year across groups.