In this study, proximal composition, mineral analysis, polyphenolic compounds identification, and antioxidant and functional activities were determined in green bean (GBF), mesquite (MF), and pea (PF) flours. Different mixtures of legume flour and wheat flour for bread elaboration were determined by a simplex-centroid design. After that, the proximal composition, color, specific volume, polyphenol content, antioxidant activities, and functional properties of the different breads were evaluated. While GBF and PF have a higher protein content (41–47%), MF has a significant fiber content (19.9%) as well as a higher polyphenol content (474.77 mg GAE/g) and antioxidant capacities. It was possible to identify Ca, K, and Mg and caffeic and enolic acids in the flours. The legume–wheat mixtures affected the fiber, protein content, and the physical properties of bread. Bread with MF contained more fiber; meanwhile, PF and GBF benefit the protein content. With MF, the specific bread volume only decreased by 7%. These legume flours have the potential to increase the nutritional value of bakery goods.