I don't believe it is the glucans that are responsible for this contribution on the part of oats, but proteins and perhaps more importantly oils (a double edged sword to be sure.) In malt, significant glucan levels are a sign of improperly conducted malting and poor modification. In most unmalted adjuncts, they are inevitably along for the ride, and must be dealt with in the mash in order to have the advantage of whatever positive contributions the adjuncts may be capable of making. Some of the effects on foam and mouthfeel often attributed to beta glucans in some of these grains, moreover, are likely actually due to other polysaccharides such as pentosans (yet again, double edged sword) which simply occur in association with the glucans in those grains. I think that rather than pursuing a probable red herring in beta glucans, it would be more advantageous to seek a well modified malt with low glucan levels and a good suite of enzymes, and supplement it with well chosen adjuncts mashed for maximum effect.