Fusarium head blight and the contamination of cereals with toxic fungal metabolites are particularly important problems in global agriculture. The increasingly frequent isolation of F. equiseti from cereal grain and the sparse information in the literature on the harmfulness of this fungus to oat encouraged us to conduct the present research. The aim of the study was to determine the susceptibility of oat genotypes to panicle infection by F. equiseti and mycotoxin content in the grain. Field experiments involving 10 oat genotypes were conducted over three years (2015–2017). Oat panicles were inoculated with a conidial suspension of F. equiseti, which reduced the kernels yield by 38.34%, the number of kernels per panicle by 31.16% and 1000 kernels weight by 12.66%. F. equiseti accumulated type A trichothecenes (T-2 and HT-2 toxins, scirpentriol, diacetoxyscirpenol, T-2 triol, T-2 tetraol) and type B trichothecenes (deoxynivalenol, 3Ac-DON, 15Ac-DON, nivalenol, fusarenone X) in kernels at an average level of 0.0616 and 0.2035 mg·kg−1, respectively. The highest susceptibility to scabs caused by F. equiseti was found for genotype POB 4901/10, whereas cv. Elegant exhibited the highest resistance to F. equiseti in terms of yield reduction after inoculation.