In a mini-greenhouse, if you mean more vegetables, why not sow some Mizuna or Mibuna greens, or Pak Choi, which you can use as a cut and come again vegetable.
Another lovely green is the watercress-like Land Cress or American Cress which will grow well in a large pot of damp compost and makes a nice spicy salad or wonderful 'watercress' soup.
Sow some 'early' variety carrots in pots as they will germinate quickly now and give you delicious baby carrots in the autumn or early winter when others are gone.
Baby beet like Chioggia or Burpees Golden have plenty of time too. Or sow and grow on some spring cabbage plants which can be planted out in autumn to give you greens next spring.