Verified answer

Look under the foil lid to make sure there's not plastic wrap, if there is remove it. cover it back up with the foil and bake, place on a baking sheet, then bake at 375 degrees for 70 minutes. Remove the lid then bake for another 10 minutes.

No need to thaw, just cook from frozen

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This guy is incorrect. I looked at my box of Stouffers frozen lasagna to give you this answer. Here's a link that will help you too -- it's the same instructions. Since you BOUGHT yours, this method should work nicely.

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Mark - you do know the difference between a frozen and unfrozen lasagna??? They are both prepared the SAME way, but one is frozen BEFORE baking in the oven. The OTHER is cooked right away. how in the world do you think it is going to take less time then??? Think about it.

Frozen Lasagna

Livvi's answer is correct, I buy those same frozen lasagnas all the time and they take almost double the oven cooking time of one made from scratch. All ingredients going into a fresh lasgna are cooked, meat is cooked, noodles boiled, so all you are really doing is heating through. takes a really long time to thaw something, and then heat it through so it is bubbly cheesy and delicious. now I am hungry for lasagna!!!

Edit: Mark, have you ever bought a frozen lasagna? It hasn't been baked yet either. you can tell cuz the grated cheese on top is still in grated form and not melted. so you've been baking your lasagnas prior to freezing?? How funny.

Leave it covered for all but the last 10 minutes

Heat it at 350 for about 30-40 minutes

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Virtually every single recipe for lasagna calls for you to cook it for less than 1 hour (50 minutes is the average). Remember, this is for UNCOOKED lasagna. Frozen lasagna is already cooked. Using the oven to thaw and bring the lasagna to serving temp will most certainly take less time than it took to originally cook it.

Virtually every single recipe for lasagna calls for you to cook it for less than 1 hour (50 minutes is the average). Remember, this is for UNCOOKED lasagna. Frozen lasagna is already cooked. Using the oven to thaw and bring the lasagna to serving temp will most certainly take less time than it took to originally cook it.

Cover w/ foil (put nonstick spray on underside!). Preheat oven to 350ºF and put lasagna in there for about an hour, maybe 70 min. Remove foil, give it another 15-20 min to firm up (will be wet) and to brown. Pull out, let sit on stove for 10 min (to firm up, cool down and set a bit) then cut and eat.