| Player Name | Pos | Ht | Wt | B-T | BornDate | Place | HiLvl | Stat Years | MLB Years | Draft Information |
| Austin O'Neal | IF | 6-4 | 220 | R-R | 1992-- | Trabuco Canyon,California | NCAA | 2010-2014 | - | |
| Cody O'Neal | P-OF | 6-0 | 185 | R-R | 1992-- | Fort Wayne,Indiana | NCAA | 2011-2015 | - | |
| Justin O'Neal | 1B | 5-8 | 180 | L-L | 1987-02-10 | Ruston,Louisiana | NCAA | 2006-2009 | - | |
| Matt O'Neal | P | 6-2 | 205 | R-R | 1989-- | Fort Smith,Arkansas | NCAA | 2010-2010 | - | |
| Sayvon O'Neal | IF | 6-2 | 165 | R-R | 1995-- | Atlanta,Georgia | NCAA | 2014-2015 | - | |
| Tucker O'Neal | P | 6-2 | 200 | R-R | 1980-- | Mount Ida,Arkansas | NCAA | 2001-2002 | - | |
| Ty O'Neal | P | 5-6 | 170 | R-R | 1998-06-01 | West Monroe,Louisiana | NCAA | 2018-2018 | - | |
| Tyus O'Neal-El | OF | 6-0 | 205 | R-R | 1998-- | Auburn,Alabama | NCAA | 2017-2018 | - | |
| Brian O'Neil | P | 6-2 | 180 | R-R | 1989-10-02 | North Reading,Massachusetts | NCAA | 2009-2012 | - | |
| Chris O'Neil | P | 5-10 | 170 | R-R | 1988-11-10 | Birmingham,Alabama | NCAA | 2008-2011 | - | |
| Michael O'Neil | P | - | - | NCAA | 2008-2008 | - | ||||
| Rob O'Neil | P | 6-2 | 195 | R-R | 1992-10-11 | Milton,Massachusetts | NCAA | 2013-2013 | - | |
| Scott O'Neil | H | - | 1988-- | - | NCAA | 2007-2007 | - | |||
| Sean O'Neil | P | 6-4 | 210 | R-R | 1981-01-18 | Oak Park,Illinois | NCAA | 2000-2002 | - | |
| Spencer O'Neil | RF | 6-4 | 185 | L-R | 1992-07-05 | Kennewick,Washington | NCAA | 2013-2015 | - | 2011-33-1019-NYA |
| Alex O'Neill | IF | 5-9 | 180 | R-R | 1992-09-13 | New York,New York | NCAA | 2014-2016 | - | |
| Barrett O'Neill | P | 6-1 | 205 | R-R | 1993-- | Ashland,Massachusetts | NCAA | 2012-2012 | - | |
| Cam O'Neill | IF | 6-3 | 185 | R-R | 1995-05-26 | Lynn,Massachusetts | NCAA | 2015-2018 | - | |
| Connor O'Neill | IF | 5-10 | R-R | Omaha,Nebraska | NCAA | 2005-2009 | - | |||
| Dan O'Neill | 1B | 6-2 | 225 | L-L | 1995-- | West Chester,Pennsylvania | NCAA | 2014-2015 | - | |
| Dan O'Neill | P | 6-4 | 215 | L-L | 1990-09-16 | Garfield,New Jersey | NCAA | 2010-2012 | - | |
| Dillon O'Neill | OF | 5-9 | 170 | R-R | 1989-- | Naperville,Illinois | NCAA | 2008-2011 | - | |
| Greg O'Neill | IF | 5-9 | 170 | R-R | 1984-05-14 | Houston,Texas | NCAA | 2005-2006 | - | |
| Jeff O'Neill | H | - | - | NCAA | 2006-2006 | - | ||||
| Jimmy O'Neill | P | 6-8 | 240 | R-R | Bradenton,Florida | NCAA | 2011-2015 | - | ||
| Player Name | Pos | Ht | Wt | B-T | BornDate | Place | HiLvl | Stat Years | MLB Years | Draft Information |
| Kyle O'Neill | IF-OF | 6-2 | 215 | R-R | Tinton Falls,New Jersey | NCAA | 2011-2011 | - | ||
| Kyle O'Neill | IF | 5-10 | 170 | R-R | 1982-10-16 | Milford,Connecticut | NCAA | 2002-2005 | - | |
| Matt O'Neill | IF-P | 198 | - | 1994-- | - | NCAA | 2001-2002 | - | ||
| Matt O'Neill | C | 6-0 | 195 | R-R | 1997-08-20 | Morristown,New Jersey | NCAA | 2015-2018 | - | |
| Michael O'Neill | P | 5-11 | 175 | L-R | 1989-06-09 | Peoria Heights,Illinois | NCAA | 2008-2008 | - | |
| Pat O'Neill | IF | 5-11 | 165 | B-R | 1998-10-13 | Eagleville,Pennsylvania | NCAA | 2018-2018 | - | |
| Ryan O'Neill | P | - | - | NCAA | 2009-2009 | - | ||||
| Ryan O'Neill | 1B | 6-1 | 220 | R-R | 1993-08-03 | Orlando,Florida | NCAA | 2013-2013 | - | |
| Sean O'Neill | OF | 6-2 | 205 | R-R | 1994-- | Huntington,New York | NCAA | 2013-2016 | - | |
| Sean O'Neill | P | 6-3 | 195 | L-L | 1987-- | Tucson,Arizona | NCAA | 2006-2007 | - | |
| Tom O'Neill | IF | 6-3 | 190 | R-R | 1994-- | Baltimore,Maryland | NCAA | 2013-2016 | - | |
| Wesley O'Neill | IF | 5-8 | 185 | - | Mississauga,Ontario | NCAA | 2008-2011 | - | ||
| Logan Onda | P | 6-0 | 185 | L-R | 1993-07-15 | Katy,Texas | NCAA | 2012-2015 | - | |
| Jim Onder | OF-P | 5-11 | 165 | L-L | Wilkins Township,Pennsylvania | NCAA | 2001-2002 | - | ||
| Cameron Onderko | IF | 5-9 | 165 | R-R | 1993-12-12 | McKeesport,Pennsylvania | NCAA | 2013-2016 | - | |
| Chris Onderlinde | IF | 5-8 | 180 | R-R | 1985-04-05 | Kalamazoo,Michigan | NCAA | 2006-2007 | - | |
| Matt Onderlinde | P | 6-1 | 190 | L-L | 1983-- | Kalamazoo,Michigan | NCAA | 2002-2005 | - | |
| David Ondo | P | 5-10 | 185 | R-R | 1986-- | Whittier,California | NCAA | 2005-2005 | - | |
| Milton Ondracek | P | - | 1958-- | - | NCAA | 1981-1981 | - | 1978- 3- 75-BOS | ||
| Al Ondrako | P | 6-1 | 175 | R-R | 1988-- | Cortland,New York | NCAA | 2007-2009 | - | |
| Doug Oney | C | 6-2 | 184 | R-R | 1989-- | Round Rock,Texas | NCAA | 2008-2011 | - | |
| Matt Oniffrey | IF | 6-0 | 185 | L-L | 1995-- | Pound Ridge,New York | NCAA | 2015-2015 | - | |
| Bryce Only | IF | 6-1 | 205 | R-R | 1994-09-10 | Jacksonville,Florida | NCAA | 2014-2017 | - | |
| Mark Onorati | OF | 5-10 | 177 | R-R | 1989-- | Williston Park,New York | NCAA | 2008-2011 | - | |
| Jeff Onstott | IF | 5-11 | 190 | B-R | 1988-08-28 | Boston,Massachusetts | NCAA | 2008-2011 | - | |
| Player Name | Pos | Ht | Wt | B-T | BornDate | Place | HiLvl | Stat Years | MLB Years | Draft Information |
| Elijah Ontiveros | C | 5-8 | 175 | R-R | 1994-- | Oxnard,California | NCAA | 2015-2017 | - | |
| Rudy Ontiveros | IF | 5-8 | 180 | L-R | 1977-05-20 | Taylor,Texas | NCAA | 2001-2002 | - | |
| Dustin Onulak | C | 5-8 | 175 | R-R | 1984-01-02 | Edison,New Jersey | NCAA | 2003-2006 | - |
