The COS-RGS305SS Gas Range: 30-Inch with Built-In Air Fry and Convection Oven
The RGS Series was built for a specific kind of cook — someone who takes daily cooking seriously, wants a gas range with genuine high-heat burner performance on the cooktop, and doesn’t want to choose between convection oven quality and built-in air fry capability when selecting a 30-inch range. The COS-RGS305SS delivers all three in a brushed stainless steel package that integrates cleanly into modern kitchen designs without demanding a specialty installation or a premium-tier budget.
Five sealed gas burners across the 30-inch cooktop cover every heat level simultaneously — from the high-output power burner that handles rapid boiling and aggressive searing to the lower-output simmer positions that hold delicate sauces and grains without cycling or fluctuating. Below the cooktop, a 4.8 cubic foot convection oven with a built-in air fry function handles the oven work that most households require across a full week of cooking. Digital display with timer keeps oven management organized. Full metal knobs control both the burners and the oven functions with the tactile precision that serious everyday cooking demands. A lower storage drawer keeps baking sheets, roasting pans, and oven accessories immediately accessible below the oven where they naturally belong. LP conversion is available for homes using liquid propane rather than natural gas.
The RGS Series sits in a specific position within Cosmo’s range lineup — it’s the Stellar Collection’s gas offering, built around the combination of cooking performance and built-in air fry that households increasingly want from a single appliance rather than supplementing a standard range with a separate countertop unit.
Why Built-In Air Fry in a Gas Range Changes How the Oven Gets Used
The built-in air fry function is the feature that most distinguishes the COS-RGS305SS from a standard gas range in its class, and understanding what it actually does and why it matters in this configuration helps clarify who this range is built for.
The Problem with Separate Air Fryers: A countertop air fryer solves the air fry function problem but creates a counter space problem. It occupies permanent real estate on a surface where every square inch matters during active cooking. It requires its own storage when not in use. It produces results in a 5-6 quart basket that limits batch size for anything beyond a single serving. And it adds another appliance to manage, maintain, and eventually replace. For households that air fry regularly, these costs accumulate into a daily friction that a built-in solution eliminates entirely.
What the Built-In Air Fry Function Actually Delivers: The air fry function in the COS-RGS305SS operates within the 4.8 cubic foot oven cavity — running the convection system at higher fan speeds that create the intense, rapid air circulation that produces crispy exterior textures with significantly less oil than conventional frying or oven baking. The result in a full oven cavity is air fry batch sizes that would require three or four rounds in a countertop basket, produced in a single oven session without managing a separate appliance.
Counter Space Recovery: For any household currently running a countertop air fryer alongside a standard range, switching to the COS-RGS305SS recovers that counter space permanently. The air fry function is always available in the oven without setup, without storage management, and without the basket-size limitation that desktop units impose. This is one of the most immediately practical quality-of-life improvements a range upgrade can deliver.
The Combination Cooking Advantage: Because the air fry function lives in the same oven as the convection bake, convection roast, and standard bake functions, a single cooking session can move between modes without transferring food between appliances. Roast vegetables at convection temperatures for the first portion of cooking, switch to air fry mode for the final minutes to develop maximum crispiness on the exterior — in the same cavity, without interruption.
Five Sealed Gas Burners
The COS-RGS305SS’s five sealed gas burners across the 30-inch cooktop deliver the simultaneous cooking capacity and immediate heat response that gas cooking is valued for.
Sealed Burner Design: All five burners use sealed construction that prevents cooking spills from reaching internal burner components. Spills that would drip into open burner mechanisms and cause corrosion, clogging, and uneven flame patterns over time stay on the cooktop surface where cleanup is straightforward. After cooking, wiping the surface and cleaning the removable burner caps addresses the mess completely — no disassembly, no internal cleaning, no accumulated residue reaching components that affect performance.
Five-Burner Capacity: Five burners on a 30-inch cooktop — the maximum configuration for this width — handles complete meal preparation simultaneously without waiting for burner availability. A protein on the power burner, two vegetable preparations on mid-range burners, a sauce on a lower burner, and rice on the fifth position all run at once. This capacity matters on weeknights when dinner needs to happen efficiently, and it matters significantly during weekend cooking or hosting when multiple dishes require simultaneous attention.
Immediate Heat Response: Gas burners respond to control adjustments in seconds — turn down the flame and heat output drops immediately, turn it up and it rises just as fast. This responsiveness makes the gas cooktop the right tool for cooking techniques that require fast heat transitions — pulling a sauce back from a boil before it breaks, increasing heat quickly when adding cold ingredients to a hot pan, managing the rapid adjustments that high-heat cooking demands.
Front Control Knobs: All five burner controls mount along the range front with full metal knob construction that holds up through years of daily use. Front positioning allows burner adjustments from a natural standing position without reaching over active cooking surfaces, reducing the burn risk that rear-mounted controls create during active multi-burner cooking sessions.
LP Convertibility: The COS-RGS305SS ships configured for natural gas. An optional LP conversion kit (sold separately) allows conversion to liquid propane for homes without natural gas service, replacing the burner orifices with LP-specific versions sized for propane’s different pressure characteristics. All five burners and the oven function identically after proper conversion.
4.8 Cubic Foot Convection Oven
The 4.8 cubic foot convection oven handles the full range of baking, roasting, and specialty cooking that a household oven needs to support across a week of regular use.
Convection Performance: The convection fan circulates heated air throughout the oven cavity, distributing heat more evenly from front to back and top to bottom than static radiant heat achieves. For multi-rack baking where consistent results across both racks matter — cookies that brown evenly regardless of position, roasts that develop consistent exterior browning on all exposed surfaces — convection’s active air distribution removes the temperature variability that static oven heat creates. Convection also reduces cooking times by 20-25% compared to conventional baking at the same temperature, which matters during weeknight cooking when dinner needs to be ready within a defined window.
Oven Cavity Cooling Ventilation: The cooling ventilation system manages heat dissipation from the oven cavity throughout cooking sessions, protecting surrounding cabinetry from heat damage and keeping the range’s exterior surfaces at comfortable temperatures during extended use. This system runs automatically and requires no separate management.
Interior Oven Lighting: Interior lighting illuminates the oven cavity during cooking, making visual monitoring possible through the oven door window without opening the door. Every door opening during baking releases heat that disrupts temperature stability and affects results — being able to assess browning progress, check liquid levels in braising dishes, and evaluate doneness visually through the window without intervention preserves cooking conditions and improves consistency.
Digital Display with Timer: The digital display shows oven temperature, selected function, and timer status from across the kitchen. The independent timer counts down without affecting oven operation — usable for stovetop tasks or any kitchen timing need simultaneously with active oven cooking. This separation is practically useful when managing multiple dishes with different timing requirements during the same cooking session.
Cast Iron Grates
The heavy-duty cast iron grates spanning the COS-RGS305SS’s full cooktop width provide the structural and thermal foundation that serious gas cooktop cooking requires.
Thermal Stability: Cast iron’s substantial thermal mass absorbs heat from burner flames and distributes it more evenly to cookware bases than lighter grate materials. This thermal buffering moderates the temperature drop that occurs when cold ingredients hit hot pans — cold chicken breast going into a hot skillet, cold pasta water added to a simmering sauce, ice-cold vegetables hitting a stir-fry wok — the cast iron grates absorb some of the thermal shock and help the pan recover temperature faster than the burner flame alone would achieve.
Continuous Surface for Heavy Cookware: The connected grate spanning all five burner positions allows sliding heavy cookware between positions without lifting — moving a full stockpot from the power burner to a simmer position, repositioning a large roasting pan during cooking. This practical advantage reduces strain and spill risk that lifting heavy, full cookware creates, particularly relevant during high-volume cooking sessions.
Durability: Cast iron withstands the physical demands that five-burner daily cooking generates without the warping or degradation that lighter grate materials develop over time. Properly maintained cast iron grates last the lifetime of the range.
Lower Storage Drawer
The full-width storage drawer below the oven provides dedicated, organized storage for the baking and roasting equipment that naturally belongs near the oven.
Practical Organization: Sheet pans, roasting racks, baking stones, cast iron pans, pizza pans, and other flat oven accessories all fit naturally in the lower drawer’s profile, accessible at floor level without searching through cabinets elsewhere in the kitchen. The equipment that goes into the oven lives directly below the oven — one motion to retrieve, one motion to return after use.
Keeping the Kitchen Organized: In kitchens where cabinet storage is limited or where baking equipment tends to migrate away from where it’s actually needed, the dedicated storage drawer below the range solves a real organization problem by giving oven accessories a natural home that keeps them consistently available.
Full Metal Knobs and Digital Touch Controls
The COS-RGS305SS uses full metal knobs for all burner controls alongside a digital display with touch controls for oven management — a deliberate combination that uses the right control interface for each cooking zone.
Metal Knobs for the Cooktop: Gas burner control through physical knobs provides immediate tactile feedback and instant visual confirmation of the setting. Full metal construction maintains this feedback quality through years of repeated use without the loosening, cracking, or softening that plastic alternatives develop near high-output gas burners. The weight and precision of metal knobs makes fine flame adjustments intuitive — you can feel the difference between settings rather than estimating by knob position alone.
Digital Touch Controls for the Oven: Oven function selection and temperature setting through the digital display allows precise settings that mechanical thermostats don’t provide. Setting exactly 375°F rather than positioning a dial between two unlabeled marks is a small daily convenience that produces more consistent baking results over time. The timer function’s digital countdown provides clear progress information without requiring secondary kitchen timers.
RGS Series: 30-Inch vs. 36-Inch
The RGS Series includes two models that share the same core specifications and design approach at different scales.
COS-RGS305SS (30-inch): Five sealed gas burners, 4.8 cubic foot convection oven with air fry, cast iron grates, digital display with timer, full metal knobs, lower storage drawer, LP convertible. The standard 30-inch configuration that fits most kitchen range openings and serves households cooking for 2-5 people regularly.
COS-RGS366SS (36-inch): Six sealed gas burners, 6.1 cubic foot convection oven with air fry, cast iron grates, digital display with timer, full metal knobs, lower storage drawer, LP convertible. The larger model adds a sixth burner and significantly more oven capacity — 6.1 cubic feet is at the high end of what 36-inch ranges provide — for households that need maximum simultaneous cooking capacity and larger oven space for high-volume meals, holiday cooking, or regular entertaining.
Choosing Between Them: The decision follows kitchen opening size and cooking volume. A 30-inch opening requires the COS-RGS305SS. A 36-inch opening with a household that regularly maxes out burner availability or needs more oven space benefits from the COS-RGS366SS’s additional capacity. Both models deliver the same Stellar Collection design, the same air fry capability, the same build quality, and the same LP convertibility — the difference is scale rather than feature set.
Installation and Kitchen Integration
The COS-RGS305SS installs as a standard freestanding range in a 30-inch kitchen range opening with straightforward gas and electrical connections.
Gas Connection: Natural gas supply connects to the range’s gas inlet through a licensed plumber or gas fitter in most jurisdictions. Standard flexible stainless steel connector lines rated for gas appliance use make the final connection between the supply line and the range inlet. Proper shut-off valves installed at the connection point allow gas service to the range to be interrupted for service or maintenance without affecting other gas appliances.
Electrical Connection: The 3-prong power cord for the electronic ignition system and digital display connects to a standard 120V household outlet positioned behind the range. This is the same electrical requirement as most gas ranges and doesn’t require dedicated high-voltage circuits.
Ventilation: Five gas burners at full output generate combustion byproducts including nitrogen dioxide, carbon monoxide, and moisture that proper range hood ventilation removes from the kitchen environment. A 30-inch range hood positioned 24-30 inches above the cooktop surface — either under-cabinet or wall mount depending on kitchen configuration — provides appropriate ventilation coverage for the COS-RGS305SS’s full burner output.
The COS-RGS305SS resolves the tension that most 30-inch gas ranges create for households who want gas cooking on the cooktop and air fry capability in the oven — requiring them to either accept a standard range without air fry and add a separate countertop appliance, or compromise on gas in favor of an electric range that includes the function. The RGS Series eliminates this compromise by delivering both in a single gas range, built to the quality standard of the Stellar Collection, at a scale that fits the kitchen opening most households actually have.