Preheat the oven to 350 degrees F (175 degrees C).

Cook ground beef, onion, and mesquite seasoning in a large skillet over medium heat until beef is no longer pink, breaking it up into crumbles as it cooks, about 10 minutes. Drain excess grease; transfer beef into a large baking dish.

Stir in baked beans, molasses, brown sugar, barbeque sauce, dry mustard powder, and cayenne pepper until any small lumps of brown sugar have dissolved.

Bake in the preheated oven until beans are bubbling and the flavors have blended, about 20 minutes.