Combine first 3 ingredients in a shallow bowl.
Pat catfish fillets dry with paper towels; brush both sides of each fillet evenly with Ranch dressing. Dredge in cornmeal mixture; lightly press cornmeal mixture onto fillets.
Cook catfish in hot vegetable oil in a large nonstick skillet over medium-high heat 3 to 5 minutes on each side or until fish just flakes with a fork. Serve immediately with lemon wedges.
Note: For testing purposes only, we used Bisquick for all-purpose baking mix.