To prep the ingredients: You don't have to grate the veggies, but I think it helps them melt into the meatloaf a little better. Make sure to thaw and squeeze the spinach out ahead of time. All the excess water will make a soggy meatloaf.
Combine all ingredients into a large mixing bowl. Mix gently to combine all ingredients into a cohesive mass. Don't squish it, or the meatloaf will come out tough.
Grease the inside of a bread/loaf pan. Add the meat mixture and make sure it pushes up against the sides. You can optionally cover with saran wrap and pop into the fridge for an hour. If so, remove from fridge 20 mins before baking.
Pre-heat oven to 350 degrees. Remove saran wrap (if resting first). Add BBQ sauce to top of meatloaf and spread evenly. Pop into over for 1 hr 15 minutes, or until internal temperature reaches 160 degrees. Remove and let cool for 10 minutes before cutting.
Note: recipe for a great BBQ sauce - https://food52.com/recipes/21962-giddy-swamp-south-carolina-mustard-barbecue-sauce