In a large saucepan, saute onion in oil until tender. Stir in the flour, basil, thyme and pepper until blended. Gradually stir in milk and Worcestershire sauce until smooth. Bring to a boil; cook and stir for 2 minutes or until thickened. Stir in the vegetables, chicken and cheese; reduce heat to low.
Meanwhile, in a large bowl, combine the flour, sugar, baking powder and salt. In a small bowl, combine the milk, oil and parsley; stir into dry ingredients just until combined.
Transfer hot chicken mixture to a greased 2-1/2-qt. baking dish. Drop biscuit batter by rounded tablespoonfuls onto chicken mixture.
Bake, uncovered, at 375° for 30-40 minutes or until biscuits are lightly browned.