Farinograph and extensograph tests were applied to determine the effect of carob fibre and oat wholemeal on the rheological properties of wheat flour dough, and characterisation of relationships between the results of the tests was performed. The applied additions of carob fibre (1–5%) and oat wholemeal (5–25%) increased the water absorption of the dough within nearly identical ranges (56–59%). Enrichment with carob fibre made the dough more rheologically stable during mixing compared to dough with oat wholemeal. In the extension test, dough with an admixture of carob fibre was more resistant, but it was less extensible than dough with oat wholemeal. Analysis of relationships of the extensograph traits to the farinograph ones revealed that longer periods of development of dough enriched with the additions under examination involved the formation of a looser dough structure, as a result of which its resistance to extension, ratio number and energy decreased and the dough extensibility increased. Opposite effects were caused by increasing farinograph elasticity and its loss. The degree of softening, negatively correlating with resistance, ratio number and energy, coupled with water absorption or with loss of elasticity, permitted their more accurate prediction. In turn, combining in a regression model of water absorption with development time or with elasticity was the most suitable for predicting dough extensibility.