Recipe: Tarragon Honey-Mustard Dressing (like Outback Steakhouse) - I think this is similar to the mustard dressing you are looking for

I have been looking for the same recipe as you, for outback house dressing. I am pretty sure that the dressing has tarragon in it, so I found these recipes on the internet, and I think they are close. Good luck.

TARRAGON HONEY-MUSTARD DRESSING

1 clove garlic, minced or pressed
1/4 cup olive oil
1 1/2 tablespoon white wine vinegar
2 tablespoons dijon-style mustard
1 teaspoon honey
3/4 teaspoon dried tarragon leaves
1/8 teaspoon pepper
salt, to taste

Combine all the ingredients, except the salt, in a small bowl and whisk until blended (or shake the ingredients in a jar). Add salt to taste.

Let stand 30 minutes or overnight to blend flavors.

Source: alt.cooking.chien/Mendi/2003

And this one claims to be a list of Outbacks ingredients:

fresh lemon juice
dijon mustard
balamic vinegar
minced garlic
dried tarragon
salt and pepper