Best Answer: Lasagna usually takes about 1 to 1-1/2 hour to cook even in a glass pan and usually that's at 350 - 375 degrees.Start it at the higher temp for the first 30 minutes, then bring it down to the lower for the last half hour or so.ating Newest Oldest. Best Answer: Lasagna usually takes about 1 to 1-1/2 hour to cook even in a glass pan and usually that's at 350 - 375 degrees. Start it at the higher temp for the first 30 minutes, then bring it down to the lower for the last half hour or so.