Preheat oven to 375℉ (190℃). Lightly grease a 9x13 baking dish or 13x18 sheet pan with nonstick cooking spray.
Place the 4 medium boneless skinless chicken breasts into the baking dish.
Quarter 2 pounds red baby potatoes or cut into bite-size pieces and spread them around the chicken.
In a small mixing bowl, melt 1/2 cup salted butter in the microwave in 15 second increments until fully melted. Stir in 1/4 cup honey, 2 tablespoons whole grain dijon mustard, 1/2 teaspoon salt, and 1/2 teaspoon dried oregano until smooth. Drizzle over the chicken and potatoes.
Bake, uncovered, in the preheated oven for about 40 minutes, until potatoes are fork-tender and chicken reaches an internal temperature of 165℉.
Give potatoes a good toss and season with 1/2 teaspoon salt and 1/2 teaspoon black pepper, or to taste before serving.