I’ve read on several threads the recommendation of using a protein rest when a large portion of the grain bill is Maris Otter. Is there a consensus opinion whether this is necessary or not.I love to use it but really have not had great efficiency, not that this number is all that important but hitting target gravities from recipes is harder for me when MO is substituted for 2 row.
Whose MO are you using? I don’t seem to have a problem with Crisp.
MO is an english variety of barley and the english method of brewing is traditionally done with a single infusion so I don’t understand why anyone would suggest you would need a p-rest on MO.
Maybe the crush is different with the bigger MO kernels?
I just finished up a bag of floor malted MO. It did work better with a protein rest but Crisp and Thomas Fausett have always worked great with just a single infusion mash.
Paul
I’ve never had the need to do a protein rest when using MO for my English or American Style Ales. I always get good head retention with MO. It’s floor malted and well modified. Not necessary IMO.
Paul - can you say which one? I have enough Warminster floor malted MO to do a bitter, and want to know if you think a protein rest is recommended.
I have used Tom Fawsett MO twice doing a bitter and both time hit my gravity on a single infusion. Crush @ .039 on my Barely Crusher, no malt conditioning. Great malt IMO.
I had to go look on Northern Brewer to get the name. I’m at work and all my notes are at home. It was Warminster.
That being said, I had a whole bag and brewed several beers with it. A few with a protein rest and a few without. There wasn’t a huge difference between the two products. I got slightly higher efficiency with the longer mash schedule but not enough to make me say it is required.
I tried the PR because I read it was a good idea with this grain. In the end I did most of the beers out of that bag using a single infusion mash and the beers are very good. I ended up concluding I would do a PR if I had time but it was really necessary.
Paul
*** Edited to clarify one point a bit.
You know, I did a PR for my very first all-grain attempt because I had read some nonsense that convinced me I “had” to… I concluded later on that certain of the many forums on the internet (especially HBT) offer more bad advice than good, and that’s when I started paying attention to who was giving the advice over at the NB forum, and then eventually I came to this forum where, though the posts are fewer, the advice is a lot more consistently worth minding.
I know what you mean, but nothing ventured nothing gained either. 
Paul
With the Warminster I will try my usual single infusion for British malts.
Isnt most common available Maris Otter fully or well modified? I thought unless a large part of the grain bill wasnt fully modified or was unmalted you wouldn’t do a protein rest. Wouldnt it lead to a thin beer? I ask because I am brewing a dry stout with Maris Otter and a lot of unmalted grain and plan on brewing a bitter with mostly Maris Otter. For the stout I plan on a protein rest and there will be no rest for the bitter.
I used to frequent NB forum. Got tired of having to disagree with people all the time. 
There was a significant discussion of problems that people were having with Fawcett MO on the NB forum. IIRC Kai was involved and provided some photos of the haze issues he was having. I also have had problems with that specific malt and have switched over to Hugh Baird instead. A friend had haze problems with Fawcett MO that were solved with a protein rest even though we all agreed that it shouldn’t have been necessary!
No it was here: http://www.homebrewersassociation.org/forum/index.php?topic=5175.0
Whether or not you should use a protein rest could vary from lot to lot of the same grain from the same brand (although most maltsters spend a lot of money and effort trying to get their malt as consistent across lots as possible.) The only way to really know is to read the malt analysis sheet for your malt.
Here’s a link to a good explanation: http://brewingtechniques.com/bmg/noonan.html
“For all-malt beers, protein values exceeding 12% (1.9% TN) indicate that the beer may haze or present mash runoff problems. European lager and British ale malts are usually below 10% protein.”
So your MO is almost certainly below 10% protein, but if you were using it in conjunction with other malts with higher protein that could bump the total amount of protein in the grist up to the point it may be less that optimal.