Despite increased interest in parenting among custodial grandmothers (CGM), there is scant research on assessing their parenting practices. With CGMs as informants we examined the factor structure for five self-report scales developed as measures of parental nurturance and discipline with birth parents, and then tested for measurement invariance by grandchildren’s age (4-< 7 vs. > 7-12). We also examined concurrent validity for these scales according to the Family Stress Model. Data were from 343 CGMs (M = 58.45, SD = 8.22) enrolled in a randomized clinical trial caring for grandchildren (GC) aged 4-12 (M = 7.81, SD = 2.56). Discipline was assessed by three scales from the Parental Behavior Inventory (Consistency, Effective, and Punitive). Nurturance was assessed by the Positive Affect Index and the Supportive Engaged Behavior scale of the Parenting Practice Interview. Confirmatory factor analysis (CFA) revealed that these scales were best represented as five distinct yet covarying factors (RMSEA = 0.055; SRMR = 0.07). Follow-up CFAs within each GC age group supported this model, with only few changes suggested by the corresponding diagnostic tests. A model with these changes was then examined for measurement invariance by CG age group, with complete measurement invariance found and all items loading onto their respective factors significantly. The five scales also correlated as expected with indices of CGM psychological distress and GC adjustment. We conclude that the scales examined here can be used meaningfully with CGM as respondents.