It sounds like you've located a bedding area (the beds in the tall grass). Prime times to hunt it would be morning evening as the deer return to bed and move out to feed. Assuming that the wind won't be blowing your scent into the bedding area.

Also be aware that bedding areas often change with seasons and food sources...in a couple months they may be bedding elsewhere to be nearer a food source, or also if fall rains make the grass too wet for them to bed.

The first thing that I would do stake out the area as much as possible to try and confirm/verify a few things: an idea of when the deer are moving....are they actually feeding in the oaks nearby....is the creek crossing into the bedding area an entrance or exit route or both (sometimes you can tell this by closely looking at the tracks, if they're all heading one way - mystery solved)

Be careful doing this - you want to be as unintrusive as possible - using optics to glass from as far away as you can. Deer are exceptionally skittish about their beds - it's their safety zone when they allow themselves to (somewhat) let down their guard and relax. The reason they do this is they trust the area as being safe. If you blow that...they WILL move.

Good luck

If it were me I would hunt that spot ASAP and in the morning (They are not necesarily using it in the morning but I tend to think the deer are bedding in the day time and feeding at night but they still will lay down at night for awhile too). I like to hunt them when I know they are there. I also expect to see them on the first visit because once you hunt it they will know you were there. They will also move after they realize you are hunting them there. If you can plan an all day watch that would be the best day to hunt them. Remember the scent going into the bedding area not only when you hunt it but also when you enter and exit the area. If you can use the river to get into the area that even better.
Thats just what I would do. I also know that I will need to change spots shortly afterward because they will move. I like to hunt fresh sign a few times then move to the next area with fresh sign. We have a lot of deer so that makes it easier.

Thanks a lot for the reply guys, its awesome you're willing to take time to share your knowledge.