Well, I'm sorry to say I may have some bad news for you. It is true in Oregon that "MOST" workers must be paid overtime after 40 hours. But there are categories that are exempt from this law and agricultural laborers are one of them! If he is a laborer performing actual farm labor 100% of the time, he is not required to be paid overtime OR minimum wage!
Per Oregon law..."Among other things, agriculture includes cultivating and tilling the soil, dairying, producing, cultivating, growing, and harvesting any agricultural or horticultural commodities, raising livestock, bees, fur-bearing animals, or poultry and any practices performed by a farmer on a farm as an incident to or in conjunction with such farming operations, including preparing for market, delivering products to storage or to market or to carriers for transportation to market."
If your husband performs work as described above, he is not entitled to overtime or required to be paid minimum wage.
HOWEVER...and this is a BIG HOWEVER - the laws go on to state that if that employee is performing non-agricultural work for another farmer that is not their employer (i.e. packing fruit for a neighboring farmer) they must be paid overtime for all hours worked over 40 in a week.
Here are a couple of links for you to look at. It will all depend on what he does for this employer as to whether he is required to be paid OT and minimum wage.
http://www.boli.state.or.us/BOLI/WHD/docs/statelawswages_english2010.pdf
http://www.boli.state.or.us/BOLI/TA/T_FAQ_Taagric.shtml
As for the fact that he is not being paid on time, that IS illegal! You can call the Wage and Hour Division and file a complaint. The employer is prohibited against retaliating for you filing a wage claim, but that may not stop him from firing your husband. However, if that happens, you make sure to let the people at the Wage and Hour Division know and they will tack on penalties, etc. to the employer!
Good luck to you and your husband! That job is undoubtedly hard enough without having to wait for a paycheck that is due!