Brewing an oatmeal stout at home

What makes an oatmeal stout different

The BJCP describes oatmeal stout as a very dark, full-bodied and roasty ale with a smooth, silky texture from oats. Typical numbers run from an original gravity of 1.045 to 1.065, a final gravity of 1.010 to 1.018, 4.2 to 5.9% ABV and 25 to 40 IBU. Colour is dark brown to black.

Oats bring proteins, beta-glucans and oils that add body and a soft mouthfeel. They do not add much flavour of their own, though toasted oats can add a light nutty note. Compared with a dry Irish stout, an oatmeal stout is fuller and a little sweeter. Our guide to brewing a stout at home covers the dry version.

A 20 litre recipe

For a 20 litre batch at about 72% efficiency, aiming for an OG near 1.054:

• 3.75 kg pale ale malt or Maris Otter (75%)
• 0.5 kg flaked or rolled oats (10%)
• 0.3 kg medium crystal malt, around 120 to 150 EBC (6%)
• 0.25 kg chocolate malt (5%)
• 0.2 kg roasted barley (4%)

Hops: an English variety such as East Kent Goldings or Fuggles at 60 minutes to reach about 30 IBU. No late hops are needed. Roast and chocolate should lead, with bitterness there only to stop the beer tasting sweet.

Plain rolled oats from an Indian grocery work well. They are steamed and flattened, so their starch is already gelatinised and they can go straight into the mash. Avoid flavoured or sweetened oats.

Mash warm and lauter carefully

Mash at 67 to 68 °C for 60 minutes. A warmer mash leaves more dextrins, which supports the full body this style needs. Hold back on going higher. Oatmeal stout should be smooth, not syrupy. Our imperial stout guide covers the bigger, sweeter end of the family.

Oats have no husk and make the mash sticky. At 10% they rarely cause trouble, but above 15 to 20% a stuck sparge becomes likely. A handful of rice hulls, around 100 to 200 g, keeps the grain bed open. If you brew in a bag, a stuck sparge is not a worry, though a firm squeeze of the bag helps drain it.

Toasting the oats

Toasting oats adds a biscuity, nutty flavour that many brewers enjoy in this style. Spread them on a tray and bake at around 150 to 160 °C for 20 to 40 minutes, stirring every 10 minutes, until golden and smelling like fresh biscuits. Let them cool for a day before brewing so harsh notes fade.

This is optional. The body comes from the oats whether you toast them or not.

Toast only what you need for the brew. Toasted oats go stale and pick up moisture quickly in humid weather, so store any extra in an airtight jar and use it within a couple of weeks.

Yeast and fermentation

Use an English ale yeast for a soft, slightly fruity character, or a clean American strain for a drier, roast-forward version. One 11 g packet of dried yeast is enough for 20 litres at this gravity. Ferment at 18 to 20 °C. Warmer than that and English strains throw too much fruit for a stout.

Roasted malts lower mash pH, which suits the hard, alkaline water common from Indian borewells. Dark beers are the one place that water can help rather than hurt. Carbonate lower than a pale ale, around 2.0 to 2.3 volumes, for a smooth mouthfeel. Serve at 10 to 12 °C to let the chocolate and coffee flavours open up.

From one recipe to the whole family

Once you have brewed a good oatmeal stout, the stout family opens up: milk stout, coffee stout, imperial stout, foreign extra stout. Each changes one or two levers, such as sugar type, roast level or strength. Our guide to brewing a coffee stout with cold brew coffee builds on this base. Learning how each grist choice shifts the beer is the step from following recipes to designing them.

Your first step: buy 500 g of plain rolled oats and toast half of it this weekend. Taste a few flakes of each and decide which you want in your first oatmeal stout.