Certified-organic cows (n = 165), according to the USDA-National Organic Program rules, were used to evaluate the effect of 2 winter housing systems (December to April) on production, SCS, body weight, BCS, incidence of frostbite, and rumination. Cows were assigned to 2 treatments (2 replicates per group): (1) outdoor (straw pack, n = 81) or (2) indoor (3-sided compost-bedded pack barn, n = 84). There were 21 cows per replicate per year for the outdoor housing and 21 and 20 cows per replicate per year for the indoor housing. Cows calved during 2 seasons (spring or fall) at the University of Minnesota West Central Research and Outreach Center, Morris, Minnesota, organic dairy. Milk, fat and protein production and SCS were recorded from monthly DHIA testing. Hygiene scores and BCS were recorded bi-weekly as cows exited the milking parlor. Frostbite incidence was collected monthly in year 2. The PROC MIXED of SAS was used for statistical analysis, and independent variables were fixed effects of year of study, season of calving (fall or spring), parity (1, 2, 3+), breed group, housing system, with replicate and cow nested within the interaction of housing system and season of calving as a random effect. Energy-corrected milk and SCS were not different for the indoor (15.8 kg/d, 2.75) and outdoor (15.5 kg/d, 2.88) housing systems. The BCS (3.38 for indoor cow vs. 3.08 for outdoor cows) within housing systems were not different. Indoor cows had greater (P < 0.05) udder hygiene scores (1.73 vs. 1.45) and greater (P < 0.05) abdomen hygiene scores (1.86 vs. 1.56) compared with outdoor cows. Incidence of clinical mastitis was greater (P < 0.05) in indoor cows compared with outdoor cows (30% vs. 13%). Frostbite incidence was not different between indoor (34%) and outdoor (21%) cows (P = 0.14). Daily rumination was 495 min/d for indoor cows and 474 min/d for the outdoor cows (P = 0.12). In summary, cows housed outdoors on straw-bedded packs did not differ from cows housed in an indoor compost-bedded pack barn for production and SCS; however, the indoor cows were dirtier and had reduced udder health compared with outdoor cows.