I’ve loved the tangy, herby drizzle from Old Spaghetti Factory for years — it’s one of those dressings that makes salads feel like a main event. This copycat version recreates that familiar balance: creamy mayo, mellow buttermilk, a hit of Romano, and a basil-forward pesto note. It’s straightforward, forgiving, and dependable when you want that restaurant finish at home.

No fancy equipment needed. You’ll whisk, season, and let it rest. Overnight refrigeration smooths the flavors and softens the basil, so patience pays off. I’ll walk you through the exact ingredients and the small techniques that make the dressing come together cleanly every time.

Read straight through for the recipe and the steps. After that I cover substitutions, storage, tools, common slip-ups, and little chef tricks I use to tune the dressing to my taste. Practical, tested, and written for busy kitchens.

What’s in the Bowl

3/4 cup vegetable oil — the fat that gives the dressing body and sheen; pour slowly when emulsifying.
1 cup mayonnaise — the creamy base and primary emulsifier; choose full-fat for best texture.
3/4 cup buttermilk — thins the dressing to pourable consistency and adds tang.
2 tablespoons grated Romano cheese — salty, sharp umami that lifts the dressing.
2 tablespoons crushed dried basil — concentrated basil flavor that mimics pesto notes without fresh leaves.
1/2 teaspoon salt — essential seasoning; taste and adjust at the end.
1 teaspoon minced garlic — bright savory bite; use fresh for best flavor.
Hot pepper sauce — heat to taste; start small and build.

Cooking Old Spaghetti Factory Creamy Pesto Dressing: The Process

In a medium bowl, place 1 cup mayonnaise and 3/4 cup vegetable oil. Whisk them together until smooth and well blended; to help the dressing emulsify, slowly pour the oil into the mayonnaise while whisking.
Add 3/4 cup buttermilk, 2 tablespoons grated Romano cheese, 2 tablespoons crushed dried basil, 1 teaspoon minced garlic, and 1/2 teaspoon salt to the bowl.
Stir the mixture until all ingredients are evenly combined and the dressing is smooth.
Add hot pepper sauce to taste, starting with a small amount and increasing until you reach your preferred level of heat. Stir to incorporate.
Transfer the dressing to a covered container or jar and refrigerate overnight (or at least 8 hours) to allow flavors to blend.
Before serving, stir or shake the dressing well and taste; if needed, adjust by adding more hot pepper sauce or a pinch more salt.

What Sets This Recipe Apart

This dressing hits a few specific notes that make it feel like the restaurant original. First, the ratio of mayonnaise to oil leans on mayo for body rather than relying solely on oil, so the texture is creamy without separating. Second, dried crushed basil stands in for pesto leaves and oil, so you get a concentrated basil note that lasts through refrigeration without turning bitter.

Romano, not Parmesan, gives the dressing a saltier, tangier edge. Buttermilk is the quiet hero: it loosens the mayonnaise just enough and adds a cultured tang that brightens each bite. Finally, the overnight rest softens raw garlic and lets the basil hydrate, producing a more cohesive flavor than serving immediately.

Vegan & Vegetarian Swaps

If you’re vegetarian, this recipe already fits — just verify the Romano is vegetarian-friendly (some cheeses use animal rennet). For vegan versions, swap components thoughtfully:

Mayonnaise: Use a vegan mayonnaise as a 1:1 swap for texture.
Buttermilk: Replace with unsweetened plain plant-based milk mixed with a teaspoon of vinegar or lemon juice, used short-term to mimic tang.
Romano: Use a fortified nutritional yeast or a vegan grated hard cheese to add umami and salt.
Hot pepper sauce and basil: Keep these as-is — they’re typically vegan.

Note: oil and dried basil stay the same. Flavors change a bit, but the structure holds.

What You’ll Need (Gear)

Medium mixing bowl — room to whisk without splashing.
Whisk — a flat whisk or balloon whisk helps emulsify evenly.
Measuring cups and spoons — accuracy matters for texture.
Rubber spatula — for scraping the bowl and getting every bit into the jar.
Covered jar or airtight container — for overnight refrigeration and shaking before serving.

Optional: an immersion blender speeds emulsification if you prefer. I usually whisk by hand; it’s quick and gives good control.

Easy-to-Miss Gotchas

Small things matter with dressings. Emulsification is delicate: pouring the oil too quickly into the mayo can cause a broken texture. Take your time during that first step. If it does separate, an immersion blender or adding a teaspoon of warm water and whisking can bring it back together.

Dried basil is potent, but if your jar is old it will taste flat. Fresh-ish dried basil gives a brighter pesto note. Also, minced garlic develops sharpness over time; letting the dressing rest overnight tames that edge. Finally, always taste after refrigeration — salt and heat levels shift slightly as flavors marry.

Spring to Winter: Ideas

This dressing is versatile through the seasons. In spring and summer, use it on a mixed greens salad with crisp cucumbers, cherry tomatoes, and grilled shrimp or chicken. It’s great on a wedge or as a dip for crudités at picnics.

In fall and winter, I use it to dress warm roasted vegetable salads — think roasted beets, Brussels sprouts, or sweet potatoes. The creaminess balances earthy roots and brightens richer winter fare. It’s also a fine sauce for a cold pasta salad with peas, cubed salami, or shredded rotisserie chicken.

Chef’s Rationale

I keep this dressing simple because the Old Spaghetti Factory original tastes clean and balanced. The mayonnaise-centric base provides immediate creaminess and helps the oil integrate without needing an egg yolk, which makes the recipe trickier to store. Buttermilk introduces gentle acidity without overpowering the basil and Romano. Choosing Romano beefs up the savory side so the dressing stands up to bold salad ingredients.

Texture is important: not too thin, not too thick. The ratios here yield a pourable dressing that clings. The overnight rest isn’t optional for me — it’s what turns a good dressing into an authentic copycat.

How to Store & Reheat

Store the dressing in an airtight jar in the refrigerator for up to one week. Because this is mayonnaise-based, don’t leave it at room temperature for long periods. Shake or stir before serving — separation of a small amount of oil is normal and corrects with a quick stir.

Do not heat this dressing. If you want a warm application, use it as a finishing sauce over warm ingredients and let the heat from the food slightly warm the dressing on contact. Otherwise, serve chilled or at refrigerator temperature.

Your Questions, Answered

Q: Can I use fresh basil instead of dried?
A: You can, but fresh basil will change the texture and intensity. Substitute about 1/3 cup packed fresh basil leaves, finely chopped, and consider reducing the buttermilk slightly if you want a thicker dressing. Since the source recipe uses crushed dried basil, the copycat flavor profile aims for that compact basil punch.

Q: My dressing is too thin. How can I thicken it?
A: Add a little more mayonnaise, a teaspoon at a time, until you reach the desired viscosity. Alternatively, chill the dressing; cold thickens it naturally.

Q: It tastes flat after refrigeration. What should I do?
A: Re-taste and adjust with a small pinch of salt or another dash of hot pepper sauce. Flavors can dull in the fridge — a little seasoning brightens them back up.

Q: Can I make this ahead for a party?
A: Yes. Make it a day ahead and refrigerate. Give it a good stir or shake before serving and adjust salt and heat as needed.

The Last Word

This Old Spaghetti Factory copycat dressing is dependable, fast to assemble, and excellent at turning ordinary salads into something memorable. It’s one of those pantry-friendly recipes you’ll come back to when you want a creamy, herby, slightly tangy dressing without fuss. Follow the steps, let it rest overnight, and don’t be afraid to tweak the heat and salt at the end.

Make a batch, tuck it into the fridge, and use it for weeknight salads, hosted lunches, or as a multipurpose dip. It’s simple, forgiving, and exactly the sort of recipe I keep bookmarked for busy days.

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Old Spaghetti Factory Creamy Pesto Dressing: Easy Copycat Recipe

A creamy copycat of the Old Spaghetti Factory's pesto dressing made with mayonnaise, buttermilk, Romano cheese, and dried basil. Simple to whisk together and refrigerate overnight for best flavor.

Prep Time10

Cook Time5

Total Time15

Course: Condiment

Servings: 10 servings

Ingredients

3/4 cupvegetable oil
1 cupmayonnaise
3/4 cupbuttermilk
2 tablespoonsgrated Romano cheese
2 tablespoonscrushed dried basil
1/2 teaspoonsalt
1 teaspoonminced garlic
Hotpeppersauce

Instructions

In a medium bowl, place 1 cup mayonnaise and 3/4 cup vegetable oil. Whisk them together until smooth and well blended; to help the dressing emulsify, slowly pour the oil into the mayonnaise while whisking.
Add 3/4 cup buttermilk, 2 tablespoons grated Romano cheese, 2 tablespoons crushed dried basil, 1 teaspoon minced garlic, and 1/2 teaspoon salt to the bowl.
Stir the mixture until all ingredients are evenly combined and the dressing is smooth.
Add hot pepper sauce to taste, starting with a small amount and increasing until you reach your preferred level of heat. Stir to incorporate.
Transfer the dressing to a covered container or jar and refrigerate overnight (or at least 8 hours) to allow flavors to blend.
Before serving, stir or shake the dressing well and taste; if needed, adjust by adding more hot pepper sauce or a pinch more salt.