Cousin Bev Crowe recently did a census search for Oneale, Oneile, Oneil, Oneal, Owneill, Owneille, Owneale, Owneal, Owneall, and Oneill. Below are the results:

1764 Frederick Co VA Rental Rolls Early VA Index: John Oneal;

1776 Frederick Co MD Sugar Land Hundred MD Early Census Index: Barton Oneal;

1776 Frederick Co MD Early Census Index: John Oneal Sugar Land Hundred;

1790 Montgomery Co: (the males 16+ include head of household, females
includes all in household) The semicolon separates the lines.
B   ONeile males 16+ = 3  Females= 4;
William ONeile  males 16+ = 2   Females = 2  Slaves = 8(?);
Wm ONeale tent.  males 16+ = 1  Females = 1;
David ONeale  males 16+ = 2  male < 16 = 1  female = 5;
John ONeil    males 16+ = 2  male <16 = 2  Females = 6

1810 Delaware Sussex Broad Creek Hundred:
Jos Oneal, 
Betsy Oneal, 
Harm(?) Oneal, there is also a
Jno Oneal: male <10=2, 16-25 = 1, 26-44 = 1, female 26-44 = 1
(it's difficult to follow the count as the census taker couldn't follow the lines);

1810 Monongalia Co VA Jos Oneal;

1810 Montgomery MD Census: Jn Oneal males: <10 = 0  >16 = 2  >26 = 1 45+ = 1  females: < 10 = 0  > 16 =1  > 26 = 1  45+ = 1;

1810 Berkley Co VA: John Oneal;

1830 Patrick Co VA John Oneil:  male 20-30 = 1,  female <5 = 3, 20-30 = 1.

1830 Ross Co OH Colerain:
John Oneal  male <5 = 1,  5-10 = 2, 30-<40 = 1, females <5 = 3, 20-30= 1;
Barton Oneal  male 20-30 = 1, 70-80 = 1, female 20-30 = 1, 60-70= 1.

1910 Ohio Champaign Co, Urbana City Miracode Index:
Barton Oneal age 83, birth place Ohio, wife Emma age 80 birth place Ohio.
I didn't realize that Barton (son of Samuel & Martha Cowgill Oneal) and his
2nd wife (Emma Strayer)lived to this age.
 

While searching through these census documents Bev found the following. 

Bev wrote: There were two statements on the census.  The below is how I read them. Not certain if "assistant"   "afilant"  "apoitant" is the correct word.