01 -
Add diced onion, bell pepper, and celery to a 5 to 6 quart slow cooker.
02 -
Place the beef chuck roast on top of the vegetables in the slow cooker.
03 -
If time allows, heat a skillet with oil over medium-high heat and brown the chuck roast on all sides for 2 minutes per side to enhance color and flavor. Then transfer to the slow cooker.
04 -
Whisk together minced garlic, tomato sauce, barbecue sauce, Worcestershire sauce, beef bouillon cubes, dried thyme, and water in a bowl.
05 -
Pour the sauce mixture evenly over the beef in the slow cooker. Cover and cook on low for 6 to 8 hours without removing the lid to ensure tender meat.
06 -
Once cooking is complete, garnish with chopped parsley if desired and serve the meat with the sauce over mashed potatoes.