I make one similar, I use:

2 pkg. Good Seasons Salad Dressing Mix
2 cans beef broth (low sodium)
1 tsp of Italian seasonings
1 jar of pepperchini's or 2 green peppers, chopped

Add to roast in crock pot. Cover and cook on low setting for 10 to 12 hours OR high setting for 4 to 5 hours.

It is so delicious! Especially served on crusty Italian rolls! I also put out provolone cheese, a dish of fresh roasted red peppers, and fresh roasted garlic. Every party I have made this for it disappears!