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Masterbuilt MPS 340/G ThermoTemp XL Propane Smoker Review

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Masterbuilt MPS 340G Thermotemp XL Smoker

Vertical gas smokers make smoking meats easy. Affordable price tags, ease of use and great results combine to make them some of the most popular residential smokers on the market.

They don’t require electricity, the vertical structure leaves a small footprint on your deck, and even a novice pitmaster or pitmistress can quickly begin impressing friends and family. With the new Masterbuilt ThermoTemp, smoking on gas just got easier. Read on.

Most outdoor cookers have inaccurate, built-in heat estimators. Vertical gas smokers notoriously use some of the cheapest, most useless “thermometers” available. These cave era gauges routinely display temperature readings that are off by 50° to 100°F. To insure your briskets and pork butts are really smoking at a low and slow temp of 225°F for 16 hours you absolutely must monitor cooking temperature with an accurate digital thermometer. Click here to learn about the importance of digital thermometers.

Thankfully, Masterbuilt’s ThermoTemp smokers don’t have cheap built-in thermometers. In fact, they don’t have any thermometers at all. Instead, they use a thermostat located inside the smoke box. The thermostat regulates the flow of gas to the burner to maintain your selected cooking temperature. Set ThermoTemp’s temperature dial from 175° to 350°F and the thermostat mounted inside will adjust the gas burner as needed, just like your indoor kitchen oven. All you need to do is add wood chunks to the wood chip tray above the gas burner and start smokin’. Learn more about gas smokers right here.

Thermostatic temperature control

A thermostat is mounted midway at the back of the smokebox.

shiny metal wall with a wired probe attached and sticking out

It senses cooking temperature and relays that info to the burner system. Set the control knob dial (below) from 175° to 350°F and the burner system will use the thermostat to maintain your set temp.

Black dial knob with orange center

Fire ThermoTemp up by pushing in the control knob and selecting a temperature. Press the piezo electric ignitor (above right) and check the burner to confirm ignition. Continue to push in  the control knob for five seconds to activate a flame sensor that controls a safety valve on the gas burner. If the flame goes out unexpectedly, The safety valve will shut off the flow of gas to the burner. A nice feature particularly on windy days.

Temperature tests

On a pleasant summer day with ambient temp in the mid eighties Fahrenheit, we clocked the following with digital thermometer probes clipped to the center of each of the four racks:

Set temp on the control knob – 175°F. Actual temp top to bottom racks – 185° to 175°F.

Set temp on the control knob – 225°F. Actual temp top to bottom racks – 240° to 222°F.

Set temp on the control knob – 325°F. Actual temp top to bottom racks – 325° to 305°F.

Set temp on the control knob – 350°F. Actual temp top to bottom racks – 355° to 326°F.

As is typical of cabinet smokers, ThermoTemp runs hotter at the top. We feel the variance from top rack to bottom rack is acceptable. Furthermore, that range of about 180° to 350°F is pretty impressive. Many gas smokers can’t easily drop below 250°F for low and slow smoking and some can’t hit 325°F to crisp skin on poultry.

Two doors are better than one

Some vertical gassers have only one door to access the smoking food on top and smoking wood on the bottom. Others, like ThermoTemp, have a separate upper door for food and lower door for tending wood. Although not essential, two doors let you replenish wood without disrupting cooking temperature in the upper smoke box. ThermoTemp’s doors clamp shut with some pretty serious hardware shown below. Like most smokers in this price range, there is no insulation in the smoker walls or to seal the doors.

Black clamping handle

Inside the upper smokebox are four 19.5 x 12 inch chrome plated racks. Some vertical gas smokers have several slots on each side so racks can be positioned at various heights. ThermoTemp racks have fixed heights, six inches apart. If you want to smoke a big turkey, you may have to remove a rack to make headroom.

Cabinet with shiny interior and four slide in racks

Close the sliding air damper at the upper-back of the cabinet to hold in smoke and moisture. Open it to release moisture for jerky and crisping poultry skin.

Shiny metal plate with black rectangular window.

An aluminized steel water pan rests in a frame at the bottom of the smokebox. It can double as a drip pan for making gravy and sauces. Here’s all you need to know about drip pans and water pans.

Shiny metal pan on a metal frame in a shiny metal cabinet

The stainless steel wood chip tray is attached to the bottom door, eliminating the need to reach in and slide it out to replenish wood. Be sure to wear gloves before lifting the HOT lid and popping in fresh wood. A word to the wise, wood chips burn up fast. Don’t fall for the popular notion about soaking wood chips in water to extend smoking time. All that does is create a little steam. Once the water steams off, those little chips burn up in a flash. Wood chunks are much better for extending smoke time. Here’s What You Need To Know About Wood, Smoke and Combustion.

Shiny metal pan with open lid attached to a metal plate.

Four to six chunks fit nicely in the tray. ThermoTemp took about ten minutes before the first puffs of smoke began wafting across our deck. With the control knob set for low and slow smoking at 225°F, our wood lasted about an hour before replenishment was needed.


What better way to kick off a smoker test than with Meathead’s Famous Last Meal Ribs Recipe? Racks in vertical gas smokers usually aren’t wide enough to lay down a whole slab of ribs flat. The ThermoTemp XL racks are 19.5 inches wide, but you don’t want food butted right up against the hot smoker walls where it can burn and disrupt airflow. The practical cooking area width is really more like 18 inches. Our slab of baby back ribs was close to 19 inches long so we cut it in half. When only cooking a small amount of food, Masterbuilt recommends using the hotter upper racks. We placed our half slabs on the second rack from the top and monitored cooking temp with a digital probe. The temp stayed steady with negligible variance and the ribs came out, smoky, moist and delicious.

Barbecued robs on a black plate

Some folks like to hang ribs and sausage from the top of their vertical smokers and some smokers have built-in hooks for this purpose. ThermoTemp does not have this feature, but you can hang hooks from the top rack, which is 22 inches from the water pan below.

Now you see it. Now you don’t

I learned a lesson long ago about grills and smokers that have windows. Clean them early and often or you’ll quickly forget that shiny, black plate was once transparent. A single slab of smoking ribs left the window hazy and discolored. If you like to look while you cook without opening the door, clean the window before or after every use. Sixty seconds with a paper towel and a few spritzes of windex cleared it up.


We smoked a load of chicken thighs at 325°F using all four racks. Aiming for crisp skin, we left the water pan empty and opened the rear air damper all the way. For our test we didn’t rotate the chicken pieces from the hot top to the cooler bottom, but the picture below shows cooking was pretty even regardless.

Chicken parts cooking on three racks inside a cabinet

The pieces on top finished a few minutes before the lower racks, but all’s well that ends well.

Tray of golden brown, cooked chicken parts.

Looking for new chicken recipes? Click here.

Pork Butt

Once again we went low and slow at 225°F with a full water pan for some smoky pork butt. The pan did double duty, serving as both a water and drip pan. And once again, ThermoTemp’s steady temp and good smoke produced delicious results with little effort. Click here for The Best Pulled Pork Recipe.

Hunk of browned, smoky meat on a cooking rack

Greasy drippings that missed the water/drip pan ended up in ThermoTemp’s slide out drip tray on the lower left side (see below).

A hand pulling out a black tray from under a black cabinet

LP gas tank goodies

ThermoTemp has a convenient LP gas retainer bracket that attaches the tank to the lower right side so you don’t have to schlep the tank and smoker separately.

A black object with an LP gas tank attached to the right side

A fuel gauge integrated with the regulator provides a rough estimate of how much juice is in the tank.

A round, white object with a round gauge

Even with this useful feature, it’s always a good idea to have a backup tank with any gas smoker. You don’t want to run out of gas at three in the morning, halfway through your 12 hour smoking session.

Although the bottom of the smoker doesn’t get extremely hot, ThermoTemp should be placed on  pavers or a grill mat when used on any surface that could be damaged by heat.


….was tedious. ThermoTemp was the first product that made us wish for unpacking directions. The thing was stuffed like a Thanksgiving turkey.

A black rectangular object laying on the ground, wrapped in clear plastic

Once unpacked, the manual directions were OK, and assembly wasn’t too bad except for the challenge of threading the thermostat and connected wire through a small, misaligned hole. And one small part that protected the thermostat wire inside the smoke box was missing. We called Masterbuilt customer service and received the missing part within several days.


Masterbuilt’s ThermoTemp line successfully offers groundbreaking use of thermostatic control on a gas smoker at an affordable price. Will Masterbuilt open the floodgates, as we have long hoped, and begin a revolution of thermostatic control, not only for gas smokers, but gas grills as well? We’ll be watching, fingers crossed.


One year limited warranty does not cover paint finish or rust.

We thank Masterbuilt for providing a Thermotemp XL for this review.

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Product Information:

  • Model:
    MPS 340/G ThermoTemp XL Propane Smoker
  • Item Price:
    $ 379.99
    *Price Subject To Change
  • Where to buy (buying from this supplier supports this website):
  • Made in USA:
  • Review Method:
    Cooked On It
    We have hands-on experience testing this product. We have also gathered info from the manufacturer, owners and other reliable sources.
  • Primary Function:
  • Fuel:
    Propane Gas
  • BTU:
  • Heat Flux:
    Heat Flux is the BTU per square inch and is a more useful measure of how much heat a grill delivers than BTU alone.
  • Primary Capacity:
    792 square inches
    Large (about 39 burgers)

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Published On: 11/5/2018 Last Modified: 7/10/2023

  • Max Good,’s Full-Time Grill Tester - Max Good is's Vice President of Product Reviews & Keeper of the Flame and is the world's only full-time reviewer of outdoor cooking equipment including smokers, grills, pizza ovens, griddles, and more.


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