How long to cook 3lb chuck roast in 350degree oven??

Understanding power levels in microwave cooking can be confusing not only to the beginning microwave cook but also to the more experienced as well. Using the proper level for each food is necessary to produce the best cooking results.
More than 9,000 people participated in our questionnaire on microwaving last fall. We have some of the results back and it's very evident that the correct power level to be used for various foods in microwaving is still a mystery to many. We listed six types of foods and asked which power level should be used for microwaving each. The foods were chuck roast, poached egg, meat loaf, cheese dip, broccoli and proofing (rising) bread.
More people missed the correct power level for microwaving a chuck roast (30 percent power) than any other food. In that category, only 11 percent of the people who had even taken a microwave class got that one correct. More than three times as many people gave the wrong power level as compared to those who answered "Don't know."
We feel that many of the complaints we get from people in their attempts to cook a chuck roast in the microwave oven are because they are doing it on too high a power level. Chuck roasts are not tender cuts of meat and need slower microwaving.
In preparing a poached egg (50 percent power) in the microwave oven, almost one-third of the respondents were able to answer the correct power level. On the other hand, about one-half of those who answered suggested the wrong power level. Again, we feel the complaints we hear concerning poached eggs in the microwave oven being like rubber balls are because many people use too high a power level for this delicate food.
Microwaving a meat loaf on the proper power level (70 percent is best but it can be done on 100 percent) was answered correctly by about two-thirds of the respondents. We feel this is one food item more people prepare successfully in comparison to other types of meat cookery in the microwave oven.
Preparing a cheese dip (70 percent power) in the microwave oven on the correct power level was answered correctly by about one-third of the respondents. Cheese has a tendency to become tough and rubbery if too high a power level is used for melting or cooking.
Proofing bread (10 percent or 30 percent power) was correctly answered by one-third of the respondents. For many who answered "Don't know," they mentioned they did not know what the word "proof" meant. Proofing is the leavening or rising of a yeast dough before baking. Although many manuals suggest 30 percent power for bread proofing, we feel using 10 percent yields better results.

what I do so it's just falls apart and great for pulled sandwiches is
set oven at 220F, season roast and put in pot with 1 or 2 cups of water, or put rack in pot so roast is NOT in water, your choice, no rack that fits in pot then get aluminum fold and crumple it up in long line and coil it to fit in bottom of pot and put roast on it.
COOK for 5 hours at 220f, you can devoure it as soon as it comes out of oven, it will just fall apart and great for making pull beef sandwiches, or let it sit for 1/2 hour and it will firm up and then it can be sliced thin or thick.
I have even done it with no water but need to be on rack or off bottom of pot as not to burn, you get a more carmilised coating on roast..
Chuck roast is tough cut of beef and need to cook for long time, 220f for 4 to 8 hrs will do the job

No at this point your roast cannot be fixed.
The future pretend your eyes your roast prior to cooking once it's cooked there's nothing you can do to tenderize it cooking it more but only make it tougher .

the temp is about right and the time is 2 3/4 hours for medium rare
in your browser bar type in ---cooking times for 3lb chuck roast--and there are recipe pages for all cuts of beef , temperatures and times

Cooking times are dependent on much more than weight. The shape of the roast, the thickness, the uniformity, the outside temperature, the quirks of your grill or oven... the only way to cook a roast properly is with a probe-type thermometer. You decide what temperature you want the center of your roast and cook it until it reaches that temperature. The lower the cooking temperature, the more evenly the roast will cook. You can Google roasting temps to give you a general idea, but if you use a recipe time, you will overcook or undercook your roast, probably, 60% of the time. Probe thermometers are cheap and reliable.

Cooking times are dependent on much more than weight. The shape of the roast, the thickness, the uniformity, the outside temperature, the quirks of your grill or oven... the only way to cook a roast properly is with a probe-type thermometer. You decide what temperature you want the center of your roast and cook it until it reaches that temperature. The lower the cooking temperature, the more evenly the roast will cook. 300 degrees will take awhile but the outcome will be excellent. You can Google roasting temps to give you a general idea, but if you use a recipe time, you will overcook or undercook your roast, probably, 60% of the time. Probe thermometers are cheap and reliable.

the norm is 2 to 2 and a half hours at 225 celcius

http://www.wikihow.com/Cook-a-Chuck-Roast

http://www.cooks.com/rec/search/0,1-0,chuck_roast_dutch_oven,FF.html

Hmmm. Let's see. Place roast On high heat In pan and sear for a minute or two on all sides. Don't cover. After roast is browned, put in oven at 300 until cooked.