The aim of this study was to find empirical models for some properties of bread dough as a function of bran concentration and particle size using D-Optimal made by Design Expert Software. Wheat flour was replaced with 0, 5, 10, 15 and 20% (w/w, flour basis) wheat bran at particle sizes of 170, 280, 425 and 750 μm. Increasing bran concentration and particle size enhanced dough water absorption. Dough arrival and development times increased, while dough stability time, tolerance to mixing and volume rising decreased as the bran particle size and concentration increased. The dough became darker, more reddish and yellower with increasing bran concentration and particle size. Dough hardness increased while cohesiveness decreased with addition of bran concentration and particle size. In general, strong correlations between dough properties with bran quantity and particle size were established. Bran concentration had stronger effect on dough properties compared to its particle size.