Difficulties with providing quality primary health care for low-income Americans have been well documented. Few studies have addressed the challenges faced by pediatric clinicians serving low-income families or whether practice-based interventions improve clinicians' ability to provide quality preventive health services. We investigated if, over time, the Healthy Steps for Young Children program affected the practices and perceptions of clinicians in pediatric primary care practices serving low-income families compared to practices serving more affluent families. Self-administered questionnaires were completed at baseline (N = 104) and at 30 months (N = 91) by clinicians at 20 pediatric practices participating in the Healthy Steps program. Practices were divided into three groups: those serving families with low, middle, and high incomes. Barriers to providing care, provision of preventive developmental services, and perceptions of care were assessed at baseline and at 30 months after introducing the program. Across all income groups and over time, clinicians were more likely to report the provision of preventive developmental health services. Clinicians in low-income practices reported increased problems with both reimbursement and time barriers; clinicians in high-income practices reported increased problems with reimbursement. At 30 months, clinicians serving low-income families reported the greatest positive changes in their perceptions about the quality of care provided by their practices. They also were more likely to strongly agree that they gave support to families and to be very satisfied with the ability of their clinical staff to meet the developmental needs of children. We found that Healthy Steps was successful in universally increasing developmental services despite the reported practice barriers for both low- and high-income practices. The Healthy Steps program enabled low-income practices to achieve similar levels of clinician satisfaction as middle- and high-income practices despite having reported lower levels at the beginning months of the program.