In the present study, the effects of different doses of oxalic acid applications on yield and quality in lettuce cultivation were evaluated. Yedikule 5107 variety was used as plant material and four different doses of oxalic acid (0-2-4-6 mM) were applied to lettuce plants from leaves. Plant weight varied between 343.02-432.57 g/plant, plant height 28.0-30.35 cm, plant diameter 26.67-28.72 cm, leaf length 21.23-22.44 cm, root collar diameter 19.11-21.49 mm and number of leaves 47.57-55.63 per plant depending on oxalic acid doses, and the highest yield was obtained from 2 mM oxalic acid application. Total chlorophyll and total phenolic contents varied between 37.47-39.31 and 67.35-103.98 mg/100g, respectively. While the highest chlorophyll value was obtained from 2 mM oxalic acid; the highest phenolic substance value was obtained from 4 mM oxalic acid application. It was determined that L*, a*, b*, and C* values varied from 47.43 to 48.76, -17.55 to -18.26, 27.89 to 28.68, and 32.95 to 34.00 depending on applications, and the highest L* value was obtained from 2 mM oxalic acid application and the highest a*, b* and C* values were observed in 2 mM and 4 mM oxalic acid applications. The antiradical values in lettuce varied between 42.36-82.64%. At the end of the study, when all these parameters were considered, it was determined that oxalic acid applications significantly and positively affect the yield and quality of lettuce.