A survey was conducted in the southern United States to investigate the occurrence of mycotoxins in pasture grasses. An initial survey in south central Florida indicated zearalenone (ZEN) in common Bermudagrass (Cynodon dactylon) as the major challenge. The survey was expanded to cover a greater geographic area and additional grass species to further explore mycotoxin exposure in grazing livestock. Grass was hand-plucked to simulate cattle foraging behavior. Samples comprised of 25–30 subsamples collected throughout each pasture were screened for the presence of mycotoxins at Activation Laboratories (Ancaster, ON, Canada; 15 mycotoxins) or Romer Labs (Union, MO; 17 mycotoxins) by the liquid chromatography tandem mass spectrometry method. Mycotoxin levels for positive samples are presented on a dry basis in parts per billion (ppb). A total of 291 samples were collected from March 2016 through January 2018, with 271 being bermudagrass, 12 were limpograss (Hemarthria altissima), 5 were bahiagrass (Paspalum notatum), one was stargrass (Cynodon spp.), and 2 were unidentified. One or more mycotoxins were detected in 200 (68.7%) samples overall. The main mycotoxin detected was ZEN in 179 (61.5%; mean of positives 1459 ppb; found in all species) of total samples and 175 (64.6%; mean 1484 ppb) of bermudagrass samples. ZEN did not occur as frequently in limpograss samples (16.7%; mean 135 ppb), but 11 (91.7%; mean 3508 ppb) tested positive for type B trichothecenes (B-Trich; including deoxynivalenol, nivalenol, and fusarenon X). Only 9 (3.3%; mean 200 ppb) of bermudagrass samples had detectable levels of B-Trich. However, type A trichothecenes (T-2 or HT-2 toxin) were detected in 43 (15.9%; mean 1492 ppb) bermudagrass samples. The preliminary results of the mycotoxin survey in Southern US grasses indicate that a variety of mycotoxins can occur at levels that may pose challenges to cattle reproduction, health, and performance. Further research is needed to better understand if specific mycotoxins are associated with certain grass species, the potential for seasonal patterns of contamination, and the greater scope of this potential challenge to grazing livestock.