transitioning from dry lot/hay to grass pasture

My mare was stalled and fed hay before I got her, so when I brought her home I put her in our dry lot with hay and have been turning her out in the pasture very slowly, increasing by half-hour increments. She's currently at 3.5 hours in the morning and 2 hours in the late evening of pasture time.

Ideally I would like her to be on the pasture 24/7. She is at an ideal weight right now, probably a bit lean, so I'm not at all concerned about her gaining too much weight. (And if she does, back to the dry lot we go.)

Anyway my question is, during the day it hasn't been a problem for me to adjust the times I go out to move her from dry lot to pasture and back, but when is it ok to leave her out overnight? I love my girl, but I'd rather not be waking up at 2 am and taking out a flashlight to move her...

If you are referring to the diet portion...at this time of year not a problem..spring is more of a concern because of the early grass growth. If you are talking about safety..if she is alone..personally I wouldn't do it. If she is with other horses then any time at this point. I hate night turn out just because the horses feel more vulnerable at night so behavior can change but many, many people have horses out without a problem. The only time I have ever had a horse get hurt was at night turnout because of daytime heat concerns.

I was more concerned about diet than behavior. She would be in that pasture alone, but she is right next to the other horses. (The other two are FAT miniatures that I'm keeping off the grass) The first few times I turned her out she stayed right next to the fence occasionally whinnying to the minis, but now she ranges all over the pasture. The fencing is "non-climb fence" (essentially thick page wire, with 2" by 4" spacing) so there is next to zero concern of her breaking out or of predators getting in (there really aren't any around here anyhow).

As far as I can tell she feels very at home in the pasture - one evening I turned her out later than usual and had to go get her in pitch dark with a flashlight. Other than giving the flashlight a quizzical glance, she didn't seem at all nervous or fearful.

Perhaps I'm being overcautious, but I'd hate for her to founder or colic because I rushed her. Heart horses are hard to find - I want to take good care of her!

Once you're able to leave her out all day, she should be fine out at night too.

Thanks

For Candy I started out with 2 hours and increased it by and hour every day. Once she got to 10 hours for a 4 days I put her out overnight and she has been on pasture 24-7 since.