Medicinal mushrooms are recognised as a source of bioactive polysaccharides and proteins with potential health benefits. This study presents the first comparative evaluation of wheat bread fortified with powdered fruiting bodies of three medicinal mushroom species: Hericium erinaceus (Lion’s Mane), Ganoderma lucidum (Reishi), and Ophiocordyceps sinensis (Cordyceps). Wheat flour was partially substituted at levels of 3–12%, and the resulting breads were analysed for (1→3)(1→6)-β-D-glucan content as well as in vitro protein and starch digestibility. Mushroom enrichment significantly increased β-glucan concentration in bread, with the greatest enhancement observed for 12% Reishi substitution (5.67% d.m.). Starch digestibility decreased across all fortified breads, accompanied by a substantial increase in resistant starch, particularly for Reishi bread (+427% relative to control). Protein digestibility was also reduced, most prominently in Cordyceps bread (−32.7 percentage points), although these products still provided up to ~52% more total protein than the control. The results confirm that incorporating medicinal mushrooms into wheat bread effectively increases its content of bioactive components, such as β-glucans, resistant starch and protein, indicating its potential as a nutrient-enriched bakery product with improved functional value.