How much your Collie eats will depend on if you have a herding dog, guard dog, companion or therapy dog. How old your dog is, their activity rate and metabolism all play into consideration.
That said, you should always feed your Collie with a high quality dry food. Snacks and table scraps should be left to a minimum. Meat should be the first ingredient to their diet. Lean chicken, beef, and salmon should suffice their dietary needs. Veggies, fruits, and nutritional supplements will help promote better growth and health with their heart and joints.
Most owners recommend 2 to 3 cups per day. This usually undermines the amount on the label of the dry kibble package. Again, if you want to know how much your Collie should be eating, then consult your veterinarian for an accurate assessment. Additionally, you should break up whatever amount you decide on to two or three meals per day. Breaking up meals reduces the chances of Bloat.
As always, you should provide your Collie with fresh drinking water.