I'd make a sort of ratatouille with onion, garlic and tomatoes and, once cool, freeze it in portion sized lots.

at this size it is a marrow. we have stuffed it with a beef mince with a mix of veg. Cut the marrow in half length ways, scoop out the seeds and add the mince mix. We often add chilli/ herbs to it. Cover with foil and bake until the marrow doesnt resist a skewer. then serve.
My daughter has cut them into 1cm rings and used them instead of lasagne sheets.

Thank you both, some interesting ideas there. The ratatouille sounds great but i can't have onions or garlic these days - old age is not for wimps!
Novel idea to use slices as lasagna - I would never ever have thought of that! Might give that a go.
I was once bamboozled into running the auction of produce after a harvest festival and there were three large marrows left that nobody wanted to bid for - managed it eventually but it was quite a challenge!