In a large bowl, combine the first 7 ingredients. Add beef and pork; mix lightly but thoroughly. On a 12x8 piece of foil, shape into a 8x5-in. loaf. Bring foil up around sides of loaf, but do not cover top of loaf.
Place trivet insert and 1 cup water in a 6-qt. electric pressure cooker. Place foil-wrapped loaf on trivet. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 45 minutes.
Let pressure release naturally for 10 minutes; quick-release any remaining pressure. A thermometer inserted in meat loaf should read at least 160°. Remove meat loaf from pressure cooker and top with barbecue sauce. Let stand 10 minutes before removing from foil and slicing.