Our old girl Heidi, the red merle, was an 85 pounder. She was a free feeder right to the end, thankfully.
Sidney, our newer boy, is about 55 pounds. We use a deli/takeout clear plastic container, the kind for 1 pound servings (about 4" diameter, 4" height), a bout 1/2 - 2/3 full twice a day, Iam's weight control dry. He's a fairly lazy slug (rare for an Aussie, but he's a mellow sweetheart), does get a few treats, but not too many.
Jasmine, our hyper labbie, is 65 - 70 pounds. She gets the same food, just a bit more. 2x/day feeding for both, I always feed them at the same time so neither can scarf up the other's.