Winter lettuces don't require heat - they will grow in open ground.

are all your tomatoes over then Hank? we still have plenty to ripen.
yes you can plant your winter lettuce now.

My 'tomato factory' is in full swing. They will keep producing fruit well into November. With your greenhouse, you can grow lettuce anytime you want. I would grow them in succession - sow new seeds every 3 weeks or so. Don't ever let them bolt or flower. That will make it taste bitter. Try growing different varieties.

Yes SG, The ones in my greenhouse have all finished, but I have 7 plants,in one of my plots nicely loaded with toms.