Probiotic products containing Lactobacillus rhamnosus GR-1 have been shown to help decrease the risk of urogenital infections, delay the decline of CD4 lymphocytes in patients with human immunodeficiency virus, and survive in the intestinal tract without stimulating immune or inflammatory responses. Cereal and pseudocereal grains can act as prebiotic agents and could be an economical way of improving the nutritional value, functional qualities, and overall health benefits of probiotic products. The purpose of this study was to measure the growth and survival of L. rhamnosus GR-1 in fermented probiotic skim milk supplemented with a grain flour over a 28-day storage period. The objective was to determine if supplementation of the grain flours would have a positive effect on the microbial vitality of L. rhamnosus GR-1 in the final product and during storage. Five probiotic skim milk samples supplemented with a grain flour were prepared: oat (3% weight to volume ratio), lentil (3% w/v), rice (3% w/v), barley (3% w/v), and quinoa (3% w/v) along with one control probiotic skim milk sample. Results showed that the oat, rice, barley and quinoa flours supported the growth of L. rhamnosus GR-1 at viable levels (10 8 CFU/mL) during the first 14 days of storage; however, only skim milk supplemented with rice flour sustained the growth over the 28-day storage period. Future studies should conduct a sensory evaluation of this fermented probiotic rice flour milk as well as study rice milk inoculated with probiotics to produce a dairy-free and possible gluten-free product.