Heat oven to 375°F. Lightly spray 13x9-inch (3-quart) glass baking dish with cooking spray.
In large bowl, stir together 3 cups shredded chicken and 2 cans (10 1/2 oz each) cream of chicken soup, garlic powder and oregano. Add 3 cups frozen vegetables and 2 cups shredded Colby-Monterey Jack cheese blend (8 oz); mix until combined. Pour into baking dish; spread in even layer.
Separate 1 can (16.3 oz) Pillsbury™ Grands!™ Flaky Layers refrigerated Butter ™ biscuits into 8 biscuits. Cut each biscuit into quarters; place in medium bowl. Drizzle with 2 tablespoons melted butter; toss to coat. Spread biscuit pieces evenly over chicken mixture.
Bake 20 to 22 minutes or until biscuit pieces are thoroughly baked and center of casserole is bubbly.