Preheat oven to 400°F and grease a baking sheet with nonstick cooking spray.
In a shallow bowl, whisk together the Bisquick mix, seasoning salt, salt, pepper, and garlic powder.
In a separate bowl, beat together the egg and milk.
Dip each tenderloin in the egg mixture, then in the Bisquick mixture. Repeat by dipping the breast in the egg a second time, followed by a second dip in the Bisquick mixture.
Place each coated breast on the prepared baking sheet. Continue dipping until all the tenderloins are coated.
Drizzle the melted butter over the top of each chicken tender.
Bake in the preheated oven for 30 minutes, until chicken is cooked through (165° internal temperature) and the breading is golden brown.