The scores
Kirkland Signature Adult Chicken, Rice & Vegetable: B (78/100) — Above average. Dual chicken proteins, quality whole grains, and a supplement stack that includes joint support at a budget price point.
Wag Chicken & Lentils: B (76/100) — Above average. Whole chicken first is a good start, but a heavy legume base, pea protein filler, and grain-free formulation hold it back.
How the ingredients compare
The top five ingredients tell the story:
Kirkland Signature: Chicken, Chicken Meal, Whole Grain Brown Rice, Cracked Pearled Barley, Chicken Fat
Wag: Chicken, Lentils, Chicken Meal, Tapioca Starch, Chicken Fat
Both formulas start with chicken, but they diverge immediately after that. Kirkland follows with chicken meal — a concentrated protein source — then two whole grains (brown rice and barley). Wag follows with lentils, then chicken meal, tapioca starch, and chicken fat. That’s the fundamental difference: Kirkland builds on a grain-inclusive foundation while Wag leans on a lentil-led, grain-free one.
The grain question matters. The FDA has been investigating a potential link between grain-free diets high in legumes and dilated cardiomyopathy (DCM) in dogs. Kirkland avoids this concern entirely with brown rice and barley — well-studied, digestible grains with their own nutritional benefits. Wag sits squarely in the DCM-flagged category.
Where Kirkland pulls ahead
Supplement stack: This is Kirkland’s biggest advantage. Glucosamine and chondroitin for joint support. These are premium additions you normally see in foods costing two to three times as much. Wag has dried chicory root for prebiotic fiber but nothing for joint health.
Quality grains over legume loading: Brown rice and barley are nutrient-dense, easily digestible carbohydrate sources with proven safety records in dog nutrition. They provide sustained energy, B vitamins, and soluble fiber.
No protein padding: Kirkland’s protein comes from chicken and chicken meal — both named animal sources. Wag uses pea protein at position six to boost protein numbers with a cheap plant isolate. When a formula needs a plant protein concentrate to hit its guaranteed analysis, it usually means the animal protein base is thinner than it looks. Shop on Amazon →
Where Wag holds its own
Wag starts with whole chicken, same as Kirkland.
Convenience is Wag’s practical advantage. It’s available on Amazon with Prime shipping, Subscribe & Save discounts, and the frictionless ordering that comes with the Amazon ecosystem. Kirkland requires a Costco membership and either a store trip or Instacart delivery. For busy households already in the Amazon ecosystem, Wag’s accessibility is a genuine factor in feeding consistency.
Wag’s formula is also simpler overall, which can appeal to owners who want a shorter, more transparent ingredient list without the supplement complexity. Shop on Amazon →
The bottom line
Kirkland Signature is the better food. A 2-point gap within the B grade reflects real differences: grain-inclusive versus grain-free, joint supplements versus none, and Wag’s pea protein padding. Both are house brands built for value, but Costco’s version delivers noticeably more nutritional depth and avoids the DCM-linked grain-free profile.
If you have access to both retailers, Kirkland is the stronger choice for your dog’s long-term health. Read our full reviews of Kirkland Signature and Wag for the complete ingredient breakdowns.
Corrected 2026-10-19: we removed claims we could not support; we corrected factual errors, and grades and score comparisons that did not match our current scores.