My two are good doers, they get 1/2 scoop fast fibre and 1/2 scoop chaff once a day at the moment but we have good grass still. When it gets really cold they will get 2 feeds a day and if I think they'll need it they'll get 1/2 scoop sugarbeet between 2 meals as well. They are a 13.1/13.2 welshie and a 14hh cob.
per day: 2 scoops Dengi Good Doer chaff, top spec comp balancer (2 mugs), about the same amount of speedi beet, and now added the same amount of crimped oats for oomph. Hay, about 5kg per night, and if in early (before 4 pm) he also gets Badminton Hay Nuggets in a ball to keep him amused. He's worked 4-5 days per week, schooling about an hour per session and hacking about the same once a week.
At tho mo my good doer's weight is just right, have manged it very carefully over the summer. The grass has alomst gone now so per day spilt into 2 feeds he is on 1 and half scopps of hi fi good doer, and 2 mugs baileys low cal, swapping to top spec thought. Garlic, salt and sunflower oil (and red cell if working hard) I will increase the hi fi to 2 scopps a day and introduce some very very water speedi beet when winter really kicks in. His (large) hey net if filled over night as he is turned at early in the mornings without hay.
I feed my good doers 1 mug Balieys Lo Cal am +pm, Alfa A Lite am +pm and I have 1 mug comp mix but up and down this depending on how much work there in and how fresh they are feeling. I'd much rather add more forage than feed through winter.
2 mugs of Bailey's lo cal and haylage gets put in the field. Can't exactly control what she she gets in haylage as they are all fed together but it's roughly one big haynet split over two lots per day. If I'm there when the haylage goes in I'll take her out - soo so mean aren't I! Also she lives out, has a light rug and a bib clip. For practical reasons she's probably ridden about 3-4 times per week in winter.
Mines a good doer in light work, 17.1hh WB, competed every weekend either unaff SJ or dressage. I just feed a large handful of readigrass, a little soaked Kwik Beet and a handful of pasture mix x twice a day. Until recently all he had for the last 15 months was Readi grass and has never looked healthier. He doesn't require anything else as his nutritional needs are not really that much. He gets pink powder for his colic more than anything, but this contains all the vits and minerals he requires as does natures own - grass! He also gets rationed haylage as this he can be prone to weight gain and I am trying continually to keep his weight down.
I think people worry far too much about what to feed their horses. Unless your horse is being worked for 40 mins + a day or is expected to event regularly then a good doer can live quite happily off grass and plenty of fibre as my boy has proved.
Very ocassionally I feel he could do with an added 'sparkle' but I can honestly say in the last couple of years I've felt like this about twice.