The objectives of this experiment were to evaluate the effects of dietary PROTEIN supplementation in lactating dairy ewe’s diets on MILK coagulation properties. MILK samples (n=126) were analyzed to assess the source of variation for rennet coagulation ability at the 6th (RCA6) and 12th hour (RCA12), MILK clotting time (MCT, s) and an index of MILK clotting time (IMCT, %). In addition, data were used to determine the influence of dietary PROTEIN source (sunflower meal (SFM) vs. rapeseed meal (RSM)) and lactating day (27, 35, 42, 49, 56, 63 and 70) on RCA6, RCA12 and MCT. Eighteen early lactation (4-10 weeks) dairy ewes from the synthetic Bulgarian dairy population breed (SBDP) were allocated into two isonitrogenous (crude PROTEIN (CP)=18%, dry matter (DM) basis) dietary treatments (n=9 per diet) formulated to contain equal amounts of fibre, energy, PROTEIN digestible in small intestines (PDI) and Ca: P ratio. The rates of MCT (s) were measured as time from rennet addition to onset of rennet-induced gel. RCA values were measured subjectively based on a scale of coagulum characteristics (score 1-3). Results showed a significant effect (P<0.05) of supplement (RSM vs. SFM) on RCA6 and a tendency at RCA12 (p=0.10). The influence on MCT and IMCT also showed such a tendency (p=0.11). Studied correlations between RCA6, RCA12 and MCT values to diet supplements at different lactation stages (days) showed no strong relationships, but the directions and strengths were permanent over the evaluated periods. We can conclude, that the investigated parameters (RCA6, RCA12, MCT and IMCT) were affected by dietary PROTEIN source (SFM vs. RSM) in regards to firmer coagulum (RCA6 and RCA12) and shorter MCT for MILK collected from ewes fed SFM vs. RSM based diets.