This is only my 2nd time growing bulb onions. So I didn't think it particularly odd that so many started to send up flower stalks. I had forgotten that this didn't happen to me last year. So I read online last night that probably due to the weather, they have stopped growing their bulbs & are now going to bloom & then go to seed . I recall that onions signalled readiness by yellowing/wilting leaves. That is how I knew when to harvest last year.
But what do I do now? Leaves are firm & green, flowers will start soon. The bulbs are immature but it's too late, I know I have to pull them up soon. Do I step on the stalks to make them wilt first or can I pull them as is? Thanks!

I believe you can harvest onions any time. Cutting the flower stalks off might help them focus more on the bulbs if you want to leave them in a bit longer. I'd only leave the flower stalks on if you want to save seeds or eat the scapes. Some onions will probably eventually die, if left in the ground all year the second year, but some should multiply and continue on into other years (perhaps especially if you cut off the flower stalks early). I've had that happen.

I'm not sure how long spring-harvested onions keep in storage, but they should be fine to eat any time. If size is your only concern, I'd say just harvest whenever you're ready to use them. If the leaves are tender enough (and not too sappy inside from the winter), they can be used for green onions (sappy ones are edible, too; they're just viscous and kind of slimy). If you've never tried onion greens on eggs, in salsa, or such, I highly recommend it.

You shouldn't need to make the stalks wilt first. You can just cut them off and eat them. They'll get too hard to eat if the flower stalks get too mature, however.

Cut the flower stems off to keep them on track to bulb. You can still let them get larger but pinch off any more buds that form. You can eat the bulbs any time, but you won't be able to store them. They don't dry down their necks well enough after bolting. Other than that, the onions should be fine.

Thanks everyone. I went right out & cut all the buds off, left the onions in the ground. Good to know that I can just pull as needed, since they won't store well now.