Preheat the oven to 350°F. Spray a loaf pan with nonstick cooking spray. Set aside.
In a large bowl, combine ground beef, ground pork, beaten eggs, parmesan cheese, parsley, kosher salt, and black pepper. Use clean hands or a wooden spoon to mix until just combined—do not overmix.
In a medium bowl, combine whole milk, breadcrumbs, minced garlic, and chopped onion. Let it sit for 2–3 minutes so the breadcrumbs can absorb the liquid.
Add the milk mixture to the meat mixture. Gently mix everything together until evenly combined. (Do not overmix)
Transfer the meat mixture to the prepared loaf pan. Shape it into a log or loaf shape, and try to keep the thickness even so it cooks uniformly.
In a small bowl, stir together barbecue sauce, honey, and grape jelly until smooth.
Pour half of the sauce mixture evenly over the top of the meatloaf.
Bake for 40 minutes.
Remove from the oven and pour the remaining sauce over the meatloaf.
Return to the oven and bake for an additional 20 minutes, or until the internal temperature reaches 160°F.
Let the meatloaf rest for about 5 minutes before slicing and serving.