Oil seed protein isolates, particularly canola protein isolate, are produced at a high purity level of at least about 100 wt % (N×6.25) by a process wherein oil seed protein is extracted from oil seed meal, the resulting aqueous protein solution is concentrated to a protein content of at least about 200 g/L and the concentrated protein solution is added to chilled water having a temperature below about 15° C. to form protein micelles, which are settled to provide a protein micellar mass (PMM). The protein micellar mass is separated from supernatant and may be dried. The supernatant may be processed to recover additional oil seed protein isolate by concentrating the supernatant and then drying the concentrated supernatant, to produce a protein isolate having a protein content of at least about 90 wt %. The concentrated supernatant may be mixed in varying proportions with at least part of the PMM and the mixture dried to produce a protein isolate having a protein content of at least about 90 wt %.