Here are well-known dog‑food companies that (in at least many of their formulas) explicitly avoid cheap fillers such as corn and wheat (many sell grain‑free or “no corn/wheat/soy” lines). I’ve included one official source for each brand so you can check specific formulas — always read the ingredient panel because some brands also sell grain‑inclusive recipes.

• Orijen / ACANA (Champion Petfoods) — many recipes are formulated without wheat, corn or soy; note Champion also offers some grain‑inclusive “Healthy Grains”/Amazing Grains” recipes. (cpftest.championpetfoods.com)
• ZIWI (ZIWI Peak) — air‑dried and canned lines marketed as grain‑free (no grains, corn, wheat). (ziwipets.com)
• Merrick — large grain‑free range; many recipes state “no grain, corn, wheat or soy.” (merrickpetcare.com)
• Blue Buffalo (Blue Freedom / Blue Basics lines) — grain‑free and limited‑ingredient lines that state “no corn, wheat or soy.” (bluebuffalo.com)
• Wellness (CORE) — CORE grain‑free lines marketed as “no fillers like wheat, corn or soy.” (wellnesspetfood.com)
• Canidae (PURE and many other lines) — many recipes formulated “without corn, wheat, soy” and with grain‑free