Cooking in the Traeger requires two primary things: temperature and time. The higher the temperature, the less time is required.
Every different meat or vegetable you cook will require a different amount of time to cook dependent upon the temperature, the specific type and size of the item. As long as the items are not touching, they will cook the same way as they would if they were the only item in the cooking chamber. Always test each item with an instant read thermometer or other suitable test to make sure it is cooked properly.
Try to estimate how long each item will take to cook and then start cooking each of those items at a suitable time before mealtime. In the instance of the beef and pork ribs, the 3-2-1 method should work for both, so start the cook about 7 hours prior to mealtime to allow time for the meat to rest after cooking. Make sure you adjust the cooking times based on internal temperature measurements rather than going by a specific time. The beef and pork might not cook at the same rate. If you cook multiple racks of ribs at the same time, they might not all cook at the same rate. Since ribs are often cooked to 203F/95C, they will take a lot longer if the grill is less than 225F/1076C. You might even need to boost the temp above that setpoint if you see the cook taking longer than expected.
If you are cooking the meat at 225F/107C (as measured by a 3rd party thermometer..not the controller setting), the potatoes will take around 2 hours to cook, so add them later in the cook. If you are cooking at a higher temperature, the cook time will be less. at higher temperatures, it will take less time. Always cook until they are fork tender rather than cooking based on time.
Corn on the cob with the husks removed will take somewhere between 1 - 1.5 hours to cook at 225F/107C, so add them to the smoker a half-hour after the potatoes. You can check to see that the corn is cooked properly by testing a few kernels with a fork. Again, do not rely on time alone.
Remember also that the cooking chamber can vary in temperature left to right, back to front, and top to bottom. Thus, things cooked in one place in the grill might not cook at the same rate as item placed elsewhere. Every grill is slightly different, so you need to get to know how your specific grill operates.
