Plant-based and alternative protein foods include processed foods derived from legumes, lentils, grains, fruits, vegetables, nuts and seeds, and their derived ingredients. The physical properties of the plant proteins and the final products are vital, since food processing is associated with a complex flow process. Rheological analysis is therefore an essential tool for evaluating constituent ingredients at different stages of the food system. The rheological properties of plant proteins could be fully characterized using various tools such as RVA, Mixolab, and Rheometer. These analytical tools can analyze the behavior of a broad spectrum of flour types, including white flour, whole grain, rice, corn, sorghum, soy, flax, amaranth, potato, buckwheat, quinoa, millet, teff, lentil flours, and legume proteins. Rheological properties are crucial for the proper use of plant-based protein ingredients in food processing. Mixolab is useful in characterizing thermo-mechanical properties of novel plant protein or protein flour mixtures. The behavior of starch and protein along with their intra-molecular interactions, and with water can be captured to reflect mixing torques force, protein weakening, starch gelatinization, and starch retrogradation. In this chapter, three protein flours (semolina, chickpea, chickpea with emulsifier) have been characterized during mixing and cooking process to evaluate their thermos-mechanical profiles. Rheological analysis can expedite innovation time for new products to market. The data obtained from rheological measurement can provide critical insights during formulation or reformulation, validating baseline ingredient performance and quality before scale-up. It is also used to screen incoming ingredients to strengthen supply chain, enabling the optimization of dry blends in baking, extrusion, frying, and compression popping platforms.