Prepare a charcoal or gas grill. Lightly spray the grill rack with vegetable oil cooking spray. The coals should be moderately hot.
Combine the bread crumbs, onions, garlic, salt, oregano, thyme, pepper, and half-and-half in a large bowl and stir well. Add the meat and, using your hands, mix well until completely blended.
Put a sheet of heavy-duty foil, about 18x24 inches, on a work surface. Place a second sheet of equal size over the first and spray the top sheet lightly with vegetable oil cooking spray.
Place the meat mixture on the top sheet of foil and form into a compact rectangular loaf about 5x8 inches. Join the sides of the top sheet of foil over the meat and fold to make a secure package. Move the package a half turn on the bottom sheet and fold this sheet again, but with the folds running in the other direction so that the meat is securely encased.
Set the package on the grill and cook for about 35 minutes. Using thick oven mitts or tongs, turn the package over and grill for about 25 minutes longer. If using a charcoal grill, add fresh coals to maintain the heat. When ready, the meat will feel firm through the foil. Unwrap the meatloaf and using 2 spatulas, transfer it to a serving platter. Slice into 1-inch-thick pieces for serving.