HEAT grill to medium heat.
COOK and stir onions in hot oil in large nonskillet on medium-high heat 5 min. or until onions are golden brown; cover. Simmer on low heat 10 min.
MEANWHILE, bring beer to boil in medium saucepan. Add bratwurst; cook 5 min. Drain bratwurst. Grill 4 to 5 min. or until heated through and browned, turning occasionally.
STIR steak sauce into onions. Top tortillas with Singles, bratwurst and onions; roll up.