What Is a Mash Bill? How Grain Recipes Shape Whiskey

At Four Roses, two grain recipes become ten whiskey recipes through a change of yeast. The producer's system makes a striking distinction: the grains define the mash bill, while the yeast helps distinguish the recipes made from it. [3]

A mash bill tells you which grains went into a whiskey and in what proportions. In American whiskey, those proportions can also help determine the legal category. They describe what went into the mash, rather than exactly how the finished bottle will taste. [1][2][9]

What a mash bill tells you

A mash bill is a whiskey's grain recipe. Historian Michael Veach defines it in practical terms: the amounts of grains used to make the beer for whiskey production. The Oxford Companion to Spirits & Cocktails describes it as a US whisky industry term, particularly associated with straight whiskey recipes such as bourbon and rye. Corn, rye, barley and wheat are the principal grains in the Companion's account. [1][2]

Corn, rye and barley name the ingredients; their percentages show how much of each went into the mix. The mash bill does not identify the yeast, the fermentation conditions or the distillation choices, all of which the Companion identifies as influences on the spirit's flavour. [1]

The Oxford Companion traces “mash bill” to mid twentieth century accounting. Distilleries commonly have a house mash bill, while some work with several. [1] A published recipe therefore offers a useful view of a producer's approach, especially when comparing whiskies made from different grain combinations. Our American whiskey guide places those recipes in the wider production process. [1]

Mash bills and American whiskey categories

For several American whiskey types, the defining grain must make up a legal minimum of the fermented mash. As checked in November 2026, US law sets the following thresholds. These are grain requirements, not complete category definitions or complete recipes: bourbon, for example, need not contain exactly 51% corn. [9]

American single malt whisky is different: the US standard requires a mash of 100% malted barley. Spirits bottled before 19 January 2030 that meet the standards in force before 19 January 2025 may still use the designation. [9]

“At least” leaves room for a distiller's recipe. Once the named grain reaches its minimum, other grains can make up the balance, as Veach explains. That freedom helps account for the different recipes found within a single category. [2][9]

A bourbon recipe containing 60% corn and another containing 75% corn both clear the corn threshold. The finished spirit must still meet the other bourbon requirements. For the complete category, beyond its grain recipe, see the bourbon guide. [3][9]

The phrase “mash bill” does not itself appear in 27 CFR part 5, and US rules do not require producers to put a complete mash bill on the label. A category name can tell you the grain minimum while leaving the exact recipe undisclosed. [9]

Two mash bills, ten recipes at Four Roses

Four Roses says it pairs two mash bills with five yeasts to make ten recipes. Verdict: Documented. The producer publishes both its grain proportions and the way it combines them with yeast, naming its two mash bills B and E. [3]

Source: Four Roses' own published process account. [3]

B has more rye and less corn than E; the barley stays the same. Both exceed the US bourbon minimum of 51% corn. Here, “higher rye” is a comparison between two published recipes, not a separate legal classification. [3][9]

Each mash bill is then paired with five yeasts to produce ten recipe combinations. Four Roses names the yeast profiles V, “Delicate Fruit”; K, “Slight Spice”; O, “Rich Fruit”; Q, “Floral Essence”; and F, “Herbal Notes”. These are the producer's descriptions of its yeast profiles, rather than independent tasting findings for every whiskey made with them. [3]

The recipe code lets you read those two choices separately. In OESV, the second letter identifies mash bill E; the fourth identifies yeast V. Knowing the code therefore reveals both the grain recipe and the yeast within Four Roses' system. [3]

The producer also describes cooking the corn first, then lowering the temperature before adding rye and barley. The percentages tell you what goes into the recipe. The cooking sequence tells you how those ingredients enter production. [3]

The source for the grain and yeast combination claim is Four Roses' undated Our Process account: https://www.fourrosesbourbon.com/our-process. Independent corroboration, a founding story and the earliest known source are not documented in the supplied material. The claim was last checked in November 2026; the exact day is not documented. [3]

Wheat in bourbon is not wheat whiskey

Maker's Mark calls soft red winter wheat “the star of our mash bill”. The producer describes using it instead of the usual rye, making its grain choice clear without publishing a complete percentage recipe in these accounts. [4][5]

That is the distinction behind “wheated bourbon”: wheat occupies the place rye holds in many bourbon recipes, while the whiskey remains bourbon. The US standard requires at least 51% corn in bourbon's mash; wheat whiskey requires at least 51% wheat. Using wheat as another ingredient in bourbon does not make it wheat whiskey. [4][9]

“Wheated” does not specify a wheat percentage, either. Current US standards do not recognise wheated bourbon as a separate legal type, so read the category alongside any recipe the producer discloses. Our guide to wheated bourbon explores that grain choice in more detail. [9]

Wheat can replace rye in a bourbon recipe, but other American whiskeys depart from the familiar three grain combination altogether. Luxco's January 2025 announcement for Penelope American Light Whiskey gives a two grain mash bill: 99% corn and 1% malted barley. Those figures describe that whiskey, rather than a general formula for American light whiskey. [6]

How grain recipes shape flavour

Grain contributes flavour. Veach reports that corn added sweetness in rye whiskey recipes, while specialty malts such as chocolate and caramel malt can contribute flavour at the cost of reduced alcohol yield. These accounts describe grain's contribution without prescribing the taste of an individual bottle. [2]

The Oxford Companion identifies mash bills, yeast, fermentation conditions, still type and sour mashing as influences on the flavour of the distillate. More of one grain does not automatically mean more of one particular flavour in the finished whiskey. [1]

Four Roses gives this principle a concrete form. In its published system, the same mash bill can be paired with five different yeasts, each with a different producer description. The grain percentages alone do not reveal which yeast was used. [3]

How much grain character survives maturation is disputed. UC Davis chemists report that wood compounds dominate after barrelling, while a distillery funded Texas study found that corn variety and farm affected the yield and flavour of new make bourbon. [10][11]

A 2019 trained sensory panel did not distinguish bourbon and rye whiskeys as categories, although producer and age had significant effects. These findings examine different aspects of production, rather than providing a single measure of grain's influence from mash to mature whiskey. Grain percentages alone cannot establish the finished flavour. [12]

How to read a published mash bill

Start with what the producer actually discloses, then put the recipe in context. These four checks make comparisons clearer.

1. Start with the category. For a US bourbon, check the corn proportion first; for rye whiskey, check the rye. Compare it with the relevant legal minimum, remembering that grain requirements form only part of the category definition. [9]

2. Check whose figures they are. Four Roses publishes complete B and E percentages. Maker's Mark identifies soft red winter wheat without giving a complete formula in the accounts cited here. Both disclosures are useful, but they offer different levels of detail. [3][4][5]

3. Compare the whole recipe. From E to B, rye rises from 20% to 35%, corn falls from 75% to 60%, and barley stays at 5%. Track the whole balance, not just the grain that catches your attention. [3]

4. Look for the next production variable. Four Roses discloses yeast as well as grain. Where a producer supplies that extra detail, use it to build a fuller understanding of the whiskey. [1][3]

Do not fill a missing percentage with a guess based on flavour. A disclosed mash bill gives precise information about the grains; it leaves other production choices to be explored.

Where to go next

• Rye Whiskey Explained: understand the category in which rye supplies the required majority grain.
• Wheat Whiskey Explained: distinguish wheat whiskey from bourbon made with wheat.
• Sour Mash: What It Is and What It Does: explore another production choice beyond grain proportions.

Sources

[1] Middleton, C. Mash bill, in Wondrich, D. and Rothbaum, N. (eds), The Oxford Companion to Spirits & Cocktails. Oxford University Press, entry reproduced on Spirits & Distilling, undated online version supplied in the verified fact sheet.
https://www.spiritsanddistilling.com/dictionary/acref-9780199311132-e-601

[2] Veach, Michael R. Mash Bills. Bourbon Veach, 4 January 2021.
https://bourbonveach.com/2021/01/04/mash-bills/

[3] Four Roses Distillery. Our Process. Undated producer account, version recorded in the verified fact sheet, November 2026.
https://www.fourrosesbourbon.com/our-process

[4] Maker's Mark. Our Story. Undated producer account, version recorded in the verified fact sheet, November 2026.
https://www.makersmark.com/story

[5] Maker's Mark. How It's Made. Undated producer account, version recorded in the verified fact sheet, November 2026.
https://www.makersmark.com/en-us/distillery/how-its-made

[6] Luxco. Penelope Bourbon releases rare American Light Whiskey. Producer announcement, 15 January 2025.
https://www.luxco.com/?p=433878

[9] Office of the Federal Register. 27 CFR part 5. eCFR full text dated 3 November 2026, particularly section 5.143.
https://www.ecfr.gov/api/versioner/v1/full/2026-11-03/title-27.xml?part=5

This desk research article was prepared from verified fact sheet TOP-A063, using its legal references, published reference material and attributed producer accounts.

Last checked: November 2026