The room temperature solitbility of a number of model proteins is assessed for a diverse set of neat ionic liquids (ILs). For two soluble protein IL pairs, lysozyme in [C2MIM][EtSO4] (1-ethy1-3-methylimidazolium ethylsulfate) and in [C2,4,4,4P][Et2PO4] (tributyl(ethyl)phosphonium diethylphosphate), protein solubility and structure at-various temperatures are probed by dynamic light scattering (assessing dissolved molecular size), tutbidirnetry (reflecting =degree of solubility), and Fourier transform infrared spectroscopy (uncovering helical secondary structure). As compared to aqueous environments, [C2,4,4,4P][Et2PO4] thermally stabilizes Protein size and secondary structure [C2MIM] [EtSO4] does the opposite. Lysozyine denatured in [C2MIM][EtSO4] does not aggregate, presumably due to an absence, of hydrophobic interactions, and the denaturation appears thermally reversible. Both ILs at room temperature are miscible with water inall proportions, but to create the corresponding ternary Mixtures with protein, the order- of mixing is important. Mixed to avoid additions of water to IL-dissolved protein, stable solutions are obtained with [C2MIM][EtSO4] at all-solvent compositions. When water is :added to IL-rich solutions, liquid liquid dembdng is noted.