Midwestpiglet, What a nice surprise for you
I know zilch about garlic but onions are a staple for us each year. They're very easy to forget. I left mine in also and have little onion sets now. You may have started your own seeds or you may have a set. Either way I'd let them grow and put in sets also just in case.
Here's a little moe info on onions than you probably ever wanted to know:
"Onions can be grown either from seeds or 'sets' (small bulbs). Seed production is cheaper and there are more cultivars to choose from. However sets require a shorter growing season (making better use of space) and omit the difficult seedling stage.
The main growing problem onions encounter is bolting. Onions are biennial: grown from seed they produce foliage in their first season, overwinter as a bulb, and then flower and die the following year. It is the cold winter temperatures that initiate flowering, and problems can occur when fluctuating temperatures trick the plant into thinking that it has experienced a winter chill when this is not the case. Onions only become receptive to winter chilling once they are a certain size. Consequently careful manipulation of sowing and planting dates lessens bolting. For example, by sowing seeds of overwintering onions in August resulting plants are large enough to survive winter cold, but small enough to be insensitive to chilling.
Bolting is more problematic with autumn sown or planted onions, as there is more risk of the bulbs being exposed to variable temperatures. However, spring cultivars are often more susceptible to bolting than autumn types. In order to obtain large bulbs from spring sowings early seed sowing is important. This is because the size of bulb the onion produces is related to the amount of foliage it produces, and as soon as days become long enough bulbing-up begins. Consequently an early sowing will give you larger bulbs, but it will also increase the risk of bolting as seedlings will become large enough to experience winter chill at an earlier date. This can be deterred by growing the onions in a heated glasshouse until weather conditions settle, or covering direct-drilled crops with fleece or glass cloches. Alternatively, delay sowings until mid-March if very large bulbs aren't required.
Onion sets have already completed one growing season and so are more sensitive to bolting. Again careful planting dates are essential (plant no earlier than mid-March) or purchase heat-treated sets where the flowering stalk has been destroyed by high temperature exposure."