Different techniques have been devised to detect herbicide resistance in weeds, and the overall aim from this study was to compare four different assay techniques for evaluating acetolactate synthase (ALS)-inhibiting herbicide resistance in sterile wild oat (Avena sterilis L.). A resistant sterile wild oat population (R) was collected from the wheat field in Kozan, Adana province, Turkey. The susceptible (S) population was collected from the border of the same field. Effects of different doses of mesosulfuron-methyl + iodosulfuron-methyl -sodium and pyroxsulam + cloquintocet-mexyl were assessed in agar based (seed and seedling) assay, Petri dish with seeds, and whole plant pot assay. In the agar based assays, the level of resistance was evaluated by measuring coleoptile and hypocotyl lengths, and survival of seedlings. Plant height and shoot dry weight were measured in the Petri dish and whole plant pot assays, respectively. Results from the dose response analyses showed that both the R and S populations were extremely sensitive to mesosulfuron-methyl + iodosulfuron in the seedling bioassay. The resistance indices (RI’s) of the R biotype treated with mesosulfuron-methyl + iodosulfuron in the agar based seed, Petri dish, and whole plant assays were 2.29, 2.63 and 4.18, respectively. The resistance indices of the R biotype treated with pyroxsulam + cloquintocet-mexyl was 3.41, 5.05 and 2.82 in the agar based seed, Petri dish, and whole plant pot assays, respectively. The agar based seed assays and Petri dish assay provided feasible, accurate, rapid, and cost effective opportunities to identify resistance in sterile wild oat.