Described are peptide analogs of glucagon, which have been modified to be resistant to cleavage and inactivation by dipeptidyl peptidase IV (DPP-IV) and to increase in vivo half-life of the peptide analog while enabling the peptide analog to have relatively balanced agonist activity at the glucagon-like peptide 1 (GLP-1) receptor and the glucagon (GCG) receptor, and the use of such GLP-1 receptor/GCG receptor co-agonists for treatment of metabolic disorders such as diabetes, non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and obesity.