Heat grill to medium heat.
Heat oil in large skillet on medium heat. Add onions; cook and stir 5 min. or until golden brown, stirring frequently. Cover; simmer on medium-low heat 10 min., stirring occasionally.
Meanwhile, grill the bratwursts 4 to 5 min. or until lightly browned and heated through, turning occasionally.
Add A.1. to onions; mix well.
Top tortillas with Singles pieces, bratwursts and onions; roll up.