Ochratoxin A (OTA) is a toxin produced both prior to harvest and during storage by Penicillium and Aspergillus species in a variety of commodities. Although several studies have been conducted in Europe and Canada examining the occurrence and concentration of OTA in cereal grains, data is lacking for the United States, where guidance levels and regulations do not exist. This study aims to fill in the knowledge gaps surrounding OTA and ochratoxigenic fungi in barley and durum and hard red spring wheat grown in the northwestern and Upper Great Plains regions of the United States. In total 2.7% (n = 37) of the 1370 samples taken over 2 consecutive years had detectable levels of OTA (0.15-9.11 ng/g) directly after harvest. The number of positive samples was significantly greater in 2012 compared to 2011. This difference may be due to weather conditions during the planting and growing seasons or simply natural variation between years. Stored barley and wheat (N = 262) had a higher prevalence (12.2%) and greater range (0.16-185.24 ng/g) of OTA compard to freshly harvested samples. Although 81.3% of the OTA-positive samples had been stored for ≥6 months, samples that had been stored for as short as 1 month also tested positive. These results underline the importance of proper storage conditions in minimizing OTA contamination. P. verrucosum was found to be the primary ochratoxigenic species in these samples. Of the 110 isolates tested, 64.7% were confirmed OTA producers. Samples containing >1 ng/g OTA had significantly more OTA-producing P. verrucosum strains than samples with undetectable OTA. Infestation rate did not correlate with OTA level. Additionally, OTA concentration did not correlate with otanpsPN, an OTA biosynthesis gene. This indicates that the concentration of P. verrucosum in a sample may increase the likelihood of contamination but is not a reliable indicator of OTA level.